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HTML Introduction


HTML documents are plain-text (also known as ASCII) files that can be created using any text editor (e.g., Emacs or vi on UNIX machines; SimpleText on a Macintosh; Notepad on a Windows machine). You can also use word-processing software if you remember to save your document as "text only with line breaks".

An element is a fundamental component of the structure of a text document. Some examples of elements are heads, tables, paragraphs, and lists. Think of it this way: you use HTML tags to mark the elements of a file for your browser. Elements can contain plain text, other elements, or both.

To denote the various elements in an HTML document, you use tags. HTML tags consist of a left angle bracket (<), a tag name, and a right angle bracket (>). Tags are usually paired (e.g., <H1> and </H1>) to start and end the tag instruction. The end tag looks just like the start tag except a slash (/) precedes the text within the brackets. HTML tags are listed below.

Some elements may include an attribute, which is additional information that is included inside the start tag. For example, you can specify the alignment of images (top, middle, or bottom) by including the appropriate attribute with the image source HTML code. Tags that have optional attributes are noted below.

NOTE: HTML is not case sensitive. <title> is equivalent to <TITLE> or <TiTlE>. There are a few exceptions noted in Escape Sequences below.

Not all tags are supported by all World Wide Web browsers. If a browser does not support a tag, it will simply ignore it. Any text placed between a pair of unknown tags will still be displayed, however.

Check out some basic tags here.



Obsolete Tags in HTML 4.0

Obsolete tags have been removed from the HTML specification. While browsers may still support obsolete tags, there is no guarantee that this support will continue.

The three tags that become obsolete in HTML 4.0 are <XMP>, <PLAINTEXT>, and <LISTING>. In all cases, replace these tags with <PRE>.

Deprecated Tags in HTML 4.0

Deprecated tags and attributes are those that have been replaced by other, newer, HTML constructs. Deprecated tags are still included in the HTML draft or recommendation but are clearly marked as deprecated. Once deprecated, tags may well become obsolete. The draft "strongly urges" the nonuse of deprecated tags.

<ISINDEX>...</ISINDEX>  

<ISINDEX> allowed a form to contain a simple string search. This action should be replaced by an <INPUT> form element.

<APPLET>...</APPLET>  

The <APPLET>...</APPLET> tag enabled the running of a Java applet. This tag has been replaced by the more encompassing <OBJECT>...</OBJECT> tag.

<CENTER>...</CENTER>  

The <CENTER>...</CENTER> tag, oddly enough, centered text or graphics. <CENTER> is deprecated in favor of <DIV> tag with the align attribute set to "center."

<FONT>...</FONT>  

<FONT>...</FONT> allowed the specification of font sizes, colors, and faces. Style sheets, rather than HTML code, have taken over character formatting duties.

<BASEFONT>...</BASEFONT>  

<BASEFONT>...</BASEFONT> set a base font size that could then be referenced for size increases or decreases. Use style sheets instead to set and reference relative font sizes.

<STRIKE>...</STRIKE> and <S>...</S>  

Both <STRIKE>...</STRIKE> and <S>...</S> created strikethrough characters. Replace these tags with style sheets.

<U>...</U>  

<U>...</U> created underlined characters. As with the tags above, use style sheets to create underlines.

<DIR>...</DIR>  

Moving away from fonts, we have the <DIR>...</DIR> tag. <DIR> describes a directory list. While originally designed to output elements in horizontal columns like UNIX directory listings, browsers formatted <DIR> lists like unordered lists. As there is no difference between the two, use a <UL>...</UL> list instead of a <DIR>...</DIR> list.

<MENU>...</MENU>  

<MENU>...</MENU> lists have also fallen by the wayside. The <MENU> tag described single-column menu lists. As with <DIR> lists, browsers made no distinction between <MENU> and <UL> lists. Use <UL>...</UL> lists instead of <MENU> ones.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/.






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