This page lists the discrepancies in HTML tag support between Netscape Navigator and Internet Explorer. These two browsers, which are in competition with each other, are both striving not only to be the better browser but to improve the quality of Web documents. There are many different features between the two, such as scripting language support and extra media "plug-ins." This chapter will focus on HTML support, because it is the most crucial element in designing and authoring documents for the greatest number of users to see.
For the most part, the browsers support the same set of tags. In cases where an element is not supported by the other browser, workarounds are easily accomplished. For example, the floating frame tag from Internet Explorer (<iframe>) uses an opening and closing tag. Browsers that don't recognize these tags ignore them, but anything between the tags is read as a regular part of the document. Therefore, you can place the same content between the tags (albeit in a different format) and not worry about withholding any information from the reader. This scheme works the same for many elements, such as <noframes> and <multicol>.
The following tags are supported only by Internet Explorer:
| HTML Tag or Attribute | Description |
|---|---|
| <bgsound> | Inserts background audio file in page |
|
<body> bgproperties=value |
Sets "watermark" background, which does not scroll with the document |
|
<body> leftmargin=n topmargin=n |
Sets the margins around the document body |
|
<caption> valign=position |
One way of setting vertical position of table caption |
| <col> | Sets text alignment for table columns |
| <colgroup> | Groups table columns |
| <comment> | Place a comment in the HTML source file |
|
<form> target=name |
Specifies a target window or frame for the output of a form |
|
<frameset> framespacing=n |
Sets amount of space between frames in the <frameset> tag |
| <iframe> | Creates floating frames |
|
<img> dynsrc=url controls loop=n start=action |
Settings for embedded video and audio clips |
|
<isindex> action=url |
Provides URL of the program that will perform the search |
|
<link> src=url rel=relation type=text/css |
Various different ways to support Cascading Style Sheets |
| <marquee> | Places scrolling marquee text in page |
| <object> |
Inserts Java applets, OLE controls, other objects into page |
| <span> | Specifies style-sheet formatting |
| <style> | Groups style elements |
|
<table> |
Sets colors for 3-D table borders in the <table>, <td>, <th>, and <tr> tags |
|
<table> frame=value |
Controls the display of outer borders of a table in the <table> tag |
|
<table> rules=value |
Controls the drawing of table rules in the <table> tag |
| <tbody> | Indicates table body rows |
| <tfoot> | Indicates table footer rows |
| <thead> | Indicates table header rows |
The following tags are supported only by Netscape Navigator:
| HTML Tag or Attribute | Description |
|---|---|
|
<frame> bordercolor=color |
Specifies color for frame border. Also works in <frameset> tag. |
|
<frameset> border=n |
Sets the amount of space between frames. |
|
<img> lowsrc=url |
Provides low-res source for faster image loading |
| <multicol> | Produces a multicolumn format. |
| <noscript> |
Provides alternative information to non-JavaScript enabled browsers. |
|
<script> src=url |
Loads an outside file containing JavaScript code |
| <spacer> | Provides whitespace objects to use in page design |
|
<textarea> wrap=style |
Specifies line-wrapping options for textareas in forms |
|
<ul> type=bullet |
Specifies bullet style for unordered lists |
In the continual struggle to be the best or most popular browser, the competitors do not always see it fit to be compatible. Here are two attributes that are used differently in each browser.
The table caption has not received fair treatment in regard to its placement by either browser. The default placement in both Navigator and Explorer is centered at the top of the table. In Netscape, align can be set to either top (the default) or bottom. There appears to be no way to get it flush right or left. In Internet Explorer, align was originally intended for horizontal placement. In version 2.0, the values could be left, right, or center. The valign attribute controlled top or bottom placement. In version 3.0, however, align is designated to do everything, taking the additional values top and bottom. Documentation for 3.0 does not list the valign attribute. You can still use it, though. It is not possible to set both a vertical and horizontal placement for the table caption with align only.
In both browsers, this attribute controls whether frames will have 3-D borders or simple rules around them. It is also usable in the <frame> tag. The trouble is that "on/off" values conflict. For Navigator, you use yes for 3-D and no for rules. In Internet Explorer, the value 1 means 3-D and 0 means rules. Go figure.