A tag that you apply to an individual character is called character tag. You can use two kinds of character tags: logical and physical. Logical character tags indicate how you want to use text, not necessarily how you want it displayed. Here's a list of some common logical character tags.
 
 

Tag	Description
<EM>	Indicates that characters should be emphasized in some way, usually  displayed with italics.
<STRONG>	Emphasizes characters more strongly than <EM>. Usually displayed in a bold font.
<CODE>	Indicates a sample of code. Usually displayed in Courier font or a similar font that allots the same width to each character.
<KBD>	Used to offset text that the user should enter. Often displayed in a  Courier font or a similar font that allots the same width to each character.
<VAR>	Indicates a variable. Often displayed in italics or underlined.
<CITE>	Indicates short quotes or citations. Often italicized by browser.

This is an example of the EM tag

This is an example of the STRONG tag

This is an example of the CODE tag

This is an example of the KBD tag

This is an example of the VAR tag

This is an example of a combination of the EM and STRONG tags

You can  also support physical character tags to indicate exactly how characters are to be formatted. Here is a list of common examples of physical character tags.
 
 

Tag	Description
<B>	Indicate the text should be bold.
<I>	Indicate the text should be italic.
<TT>	Indicate the text should be used with a font like Courier that allots the same  width to each character.
<BIG>	Indicate the text should be displayed in a big font. Available only in HTML 3.0 or above.
<SMALL>	Indicate the text should be displayed in a small font. Available only in HTML 3.0 or above.
<SUB>	The text should be displayed as a subscript, in a smaller font if possible  Available only in HTML 3.0 or above.
<SUP>	The text should be displayed as a superscript, in a smaller font if possible  Available only in HTML 3.0 or above.

Some browser also support <U> tag for underlining text, but other browsers might not show underlining , so use it cautiously.

This is an example of the B tag

This is an example of the I tag

This is an example of the TT tag

This is an example of the BIG tag

This is an example of the small tag

This is an example of the _{sub tag}

This is an example of the ^{SUP tag}
 

Given the presence of both logical and physical character tags, which should you use to display some text in an italicized font:
<EM> or <I>?  The answer depends on who will view your web page. Some browsers like the UNIX browser Lynx, are text based and cannot display italics. These browsers ignore the <I> tag, so emphasis you want to place on a certain piece of text is lost. In this case you would use logical tag. On the other hand, if you decide that only graphical browser such as Netscape Navigator or Internet Explorer will access your page, you might  want to use a physical tag since it more explicitly defines what resulting text looks like on the browser.