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LIS900C: HTML structural tags Thomas Krichel and Jeremiah C. Trinidad 2003-05-13.

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Presentation on theme: "LIS900C: HTML structural tags Thomas Krichel and Jeremiah C. Trinidad 2003-05-13."— Presentation transcript:

1 LIS900C: HTML structural tags Thomas Krichel and Jeremiah C. Trinidad

2 feeling sloppy? Thomas Krichel is a very strict professor. Therefore he wants to teach strict HTML. But actually he will only check if the pages validate, but not prescribe a particular DTD. So you can also use the loose DTD I will teach the constraints of the strict DTD.

3 today I will do a list of tags that describe the structure of the page. I will only do the tags of the strict DTD The loose DTD has more tags, but all the functionality of these tags is best done with style sheets. Tomorrow Thomas Krichel will show you how to add presentational elements through style sheets. Thus, the pages created today will look rather boring because I will not cover fancy style.

4 today You can start from empty.html, the file that validates, and copy it to test.html cp empty.html test.html nano test.html Then you can change test.html to try out the tags as I discuss them here.

5 things I do not cover input forms frames mouse event attributes clickable image maps some fine points of table construction. at the end you will be happy that I did not…

6 the tag appears after the DTD declaration encloses the html contents has required contents and. the "dir" attribute says in which direction the contents is rendered. The classic value is "ltr", "rtl" is also valid. the "lang" attribute says in which language the contents is. Use ISO 639 codes, e.g. lang="en- us"

7 the tag appears right after the tag to give metadata about the document. It may have the "dir" and "lang" attributes as the html tag does. must contain a tag. It may also contain and, as well as – to set a base URL – to give metadata –and some other stuff that I do not cover

8 the tag (required) appears in the, defines the title of the document takes "dir" and "lang" attributes. The title is used by the browser in a special manner, e.g. as bookmark default title. Google uses the title as anchor text to your web page. A good title is therefore very important! Bad ideas for titles –section 1 –home page

9 the tag in Appears in the of the page. It is used to give style sheet information for the whole document. The "type" attribute give what type of style it is, usually it takes the value "text/css" for CSS. Example h1 {text-align: center} More on CSS tomorrow!

10 the tag in appears in the of the page. create a link between the current page and others mainly used to create a link between the page and a style sheet in a separate page as in where url is a URL details to be discussed tomorrow. Other usages are possible but rare.

11 other values of "rel" attribute Alternate Stylesheet Start Next Prev Contents IndexGlossary Copyright Chapter Section Subsection Appendix Help Bookmark

12 the tag in This can be used to include metadata in the header. It has an attribute "name" for the property name It has an attribute "content" for the property values There is no standard set of names and values. Example:

13 the tag in There is also a special way to pass http headers to the client The "http-equiv" lets you set http variable and send them to the client. Example: will tell the server to tell the browser that the page is written in html. more on this later, when we discuss http.

14 the tag Can fix the baseline URL for all the relative links in the document. Within the confines of what we are working with, I do not see a reason for you to use it.

15 the tag This encloses the contents of the page as opposed to its header. Strict validation requires it. Strict validation limits the document to have only one body. It admits the "lang" and "dir" attributes, as well as some others that we will discuss now. These fall into a group of attributes we call "usual suspect attributes"

16 usual suspects attributes: id This attribute assigns a name to an element. This name must be unique in a document. In the element, this requirement is superfluous, of course. The id attribute has several roles in HTML, including As a style sheet selector. As a target anchor for hypertext links.

17 usual suspects attributes: class The class attribute is a friend of the "id" attribute. It assigns one or more class names to a tag; the tag may be said to belong to these classes. A class name may be shared by several tags. It is like placing the tag instance into a set of tags. The class attribute has several roles in HTML, but it is most useful as a style sheet selector, when you want to assign style information to a set of tags.

18 Example for "class" There was a young man from Peru Whose limericks stopped at line two This is really a stupid limerick. Let us look at another There was a young from from Japan Whose limericks would never scan And when they asked why He said it is because I Try to put as many words into the last line as a possibly can

19 usual suspects attributes: title The "title" attribute sets a title in use with the element. There is no prescribed way in with the title is being rendered by a user agent. Sometimes it is shown as a tool tip, i.e. something that flashes up when the mouse is rolled over it. This is not to say that the "title" attribute is for flashers only.

20 usual suspects attributes: style Use the "style" attribute to give style information to a particular element. This will be more discussed tomorrow, for the moment, you can relax and forget about it.

21 summary: usual suspects attributes To summarize, we have a group of usual suspects attributes These attributes can be used with almost all elements. The ones that we mention here are –dir– lang– id – class –title– style There are other attributes that can be universally used, called "event attributes", but they have to do with scripting, they are therefore not studied in this course.

22 the and tags The tag allows you to set arbitrary block level divisions in your document. It admits the usual suspects attributes. It also admits the "align" attribute. "align" sets alignment of contents. It can take the value –"left"this is the default –"right" –"center" The tag is like but it signals the start and end of a paragraph.

23 The tag This is another tag for arbitrary divisions, but it operates on inline content. This in contents that is put is lines horizontally, rather than block-level contents, that is put in vertically. Admits usual suspect attributes, but not "align" because it is put into the line with the contents next to it. More on that tomorrow.

24 header tags Headers to Simple form of text formatting Vary text size based on the headers level Actual size of text of header element is selected by browser. Results can vary significantly between user agents. All admit the usual suspects attributes

25 Now let us play Create a document with various headers Include different alignments Compare results in a couple of user agents. and then I will do images and multimedia

26 tag create a horizontal rule admits the usual suspect attributes other attributes have been deprecated, i.e. are allowed in the loose DTD but not the strict one.

27 the tag "src" attribute says where the image is "alt" attribute give a text to show for user agents that do not display image. It may be shown by the user agents as the user highlights the image. It is limited to 1024 characters. "longdesc" attribute is the same as "alt" but does not have the length limitation.

28 the tag II "width" attribute gives the user agent a suggestion for the width of the image. "height" attribute gives the user agent a suggestion for the height of the image both can be expressed –in pixels, as a number –in %age of the current display width of course supports the usual suspects attributes.

29 contents-based style tags encloses abbreviations encloses accronyms encloses citations encloses computer code snippets encloses things being define encloses emphasized text encloses text typed on a keyboard encloses literal samples encloses strong text encloses variables all admit the usual suspects attributes

30 physical style tags encloses bold contents encloses big contents encloses small contents encloses italics contents encloses subscripted contents encloses superscripted contents encloses typewriter-style contents all admit the usual suspects attributes

31 the tag is used to create a line break which of the usual suspect attributes does it not admit? Instead it has the clear attribute that can take the values "left", "right" and "center" and "all". This prevents textual content to float around other content. Admits usual suspects attributes. It is not required to close the tag, but Thomas Krichel recommends to write it as, this closes the tag.

32 the tag encloses contents that is to be rendered with the characters and line breaks just like in the source text. Markup is still allowed, but tags that do spacing should not be used, obviously. If you want to render HTML, quote –as> –&as & It admits the usual suspects and a width attribute setting the number of characters per line.

33 and tags quotes a paragraph make a short quote inside a paragraph both admit a "cite" attribute that take the value of a URL of the source of the quote. The also admit the usual suspect attributes.

34 the tag opens a hyperlink, contents of tag is the anchor text, it is limited to text only "href" attribute has the target URL "hreflang" has the language of the target "type" attribute gives the MIME-type of the target Some other attributes for which we have no use –coords–shape–accesskey–tabindex and of course, admits the usual suspects attributes

35 the tag II it admits the "rel" attributes to specify the relationship between the current document and the link target, as well as the "ref" attribute to specify the reverse. This is not currently well supported by the browsers.

36 linking within a document If you have the "id" attribute (one of the usual suspects) set to id on an element in a document at a URL URL, you can make the element the target of a link. You use the URL URL#id for this purpose. The "name" attribute can also be used for this purpose, instead of "id", but this is only allowed for historical reasons. If the document linked to is the current document, you dont need to reference its URL.

37 list tags: and creates an ordered list. ordered list of course, they also support the usual suspects attributes

38 the tag It marks each item of a list. it is usually not closed. it admits the "type" attribute, so you can style each item differently it admits a "value" attribute, so you can give each item a different numerical value in an ordered list. You can do that if you want to confuse the hell out of your users. The value of "value" must be a number, of course. admits the usual suspects.

39 definition lists tags encloses a definition list encloses the term that is being defined encloses the definition All admit the usual suspects.

40 Slides prepared by K.Clarck Tables A table is a matrix formed by the intersection of a number of horizontal rows and vertical columns. Column 1 Column 2 Column 3 Row 1 Row 2 Row 3

41 Slides prepard by K.Clark Tables (continue…) The intersection of a column and row is called a cell. Cells in the same row or column are usually logically related in some way. Column 1 Column 2 Column 3 Row 1 Row 2 Row 3 Cell

42 the tag encloses a table The "summary" attribute provides a summary of the table's purpose and structure for user agents rendering to non-visual media such as speech and Braille. The width attribute specifies the desired width of the entire table and is intended for visual user agents. When the value is a percentage value, the value is relative to the user agent's available horizontal space.

43 the frame attribute of This attribute specifies which sides of the frame surrounding a table will be visible. Possible values: –void: No sides. This is the default value. –above: The top side only. –below: The bottom side only. –hsides: The top and bottom sides only. –vsides: The right and left sides only. –lhs: The left-hand side only. –rhs: The right-hand side only. –box: All four sides. –border: All four sides.

44 the "rules" attribute of This attribute specifies which rules will appear between cells within a table. Possible values –none: No rules. This is the default value. –groups: Rules will appear between row groups only. –rows: Rules will appear between rows only. –cols: Rules will appear between columns only. –all: Rules will appear between all rows and columns We will not study groups in the remainder of the lecture We will now study the alignment attributes

45 alignment: the "align" attribute The "align" attribute specifies the alignment of data and the justification of text in a cell. Possible values: –left: Left-flush data/Left-justify text. This is the default value for table data. –center: Center data/Center-justify text. This is the default value for table headers. –right: Right-flush data/Right-justify text. –justify: Double-justify text. –char: Align text around a specific character. If a user agent doesn't support character alignment, behavior in the presence of this value is unspecified.

46 alignment: the "valign" attribute The "valign" attribute specifies the vertical position of data within a cell. Possible values: –top: Cell data is flush with the top of the cell. –middle: Cell data is centered vertically within the cell. This is the default value. –bottom: Cell data is flush with the bottom of the cell. –baseline: All cells in the same row as a cell whose valign attribute has this value should have their textual data positioned so that the first text line occurs on a baseline common to all cells in the row. This constraint does not apply to subsequent text lines in these cells.

47 alignment: "char" and "charoff" The "char" attribute specifies a single character within a text fragment to act as an axis for alignment. The default value for this attribute is the decimal point character for the current language as set by the "lang" attribute. The "charoff" attribute specifies the offset to the first occurrence of the alignment character on each line. If a line doesn't include the alignment character, it should be horizontally shifted to end at the alignment position. The direction of offset is determined by the current text direction, as set by the "dir" attribute. (obscure)

48 alignment: the cell spacing The "cellspacing" attribute specifies how much space the user agent should leave between the left side of the table and the left-hand side of the leftmost column, the top of the table and the top side of the topmost row, and so on for the right and bottom of the table. The attribute also specifies the amount of space to leave between cells. The "cellpadding" attribute specifies the amount of space between the border of the cell and its contents. If the value of this attribute is a pixel length, all four margins should be this distance from the contents. These attributes can be set to pixels or percentages.

49 encloses a table row it admits the alignment attributes it admits the usual suspects attributes.

50 the tag encloses a cell in a table that is not a header cell It admits the alignment and usual suspects attributes It has an "abbr" attribute for abbreviated contents. Its "rowspan" and "colspan" attributes say how many rows or columns the cell spans. It has a "headers" attribute specifies the list of header cells that provide header information for the current data cell. The value of this attribute is a space-separated list of header cell "id" attribute values.

51 the element encloses a header cell It admits the same attributes as, but "headers" does make no sense here. Instead, we have a "scope" attribute that specifies the set of data cells for which the current header cell provides header information. It can take the values –row: The current cell provides header information for the rest of the row that contains it. –col: The current cell provides header information for the rest of the column that contains it. –rowgroup: The header cell provides header information for the rest of the row group that contains it. –colgroup: The header cell provides header information for the rest of the column group that contains it.

52 more on tables… Yes, there are some fine points like the grouping and axis attributes. But for all but the most sophisticated tables, what we have covered is enough.

53 Special Characters Inserted as an entity reference –Format can be &code; Ex. & –Insert an ampersand –Codes often abbreviated forms of the character –Codes can be in hex form Ex. & to insert an ampersand has the list

54 Thank you for your attention!

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