The Underscore Hack
Let’s start with three simple facts — as Petr Pisar found out.
- The underscore (“_”) is allowed in CSS identifiers by the CSS2.1 Specification
- Browsers have to ignore unknown CSS properties
- MSIE 5+ for Windows ignores the “_” at the beginning of any CSS property name
Therefore, a CSS definition, e. g. _color:red is:
- Correct, for CSS 2.1 specification allows it (even if software validators, knowing only older version CSS 2.0, say it’s a bug: they are wrong, it’s correct).
- Ignored in any browser but WinIE
- Treated as color:red in WinIE
Thus, this IE’s bug/feature is very simple and clear way to set CSS properties for WinIE only (MacIE doesn’t have this bug/feature). It’s easy to fix e. g. mis-implemented position:fixed in WinIE (see the example).
</p>
<h1>menu {</h1>
<p>position: fixed;
_position: absolute;
…
}
Same method may be used to fix the min-height property missing in WinIE (see the example 2):
</p>
<h1>box {</h1>
<p>min-height: 300px;
height: auto;
_height: 300px;
…
}
Note: This uses another WinIE’s bug, treating overflow:visible as height:auto. For details, see the article “The “min-height” Hack”.
I tested it in Windows’ MSIE 5, 5.5, 6, and Opera; Mac OSX’s MSIE 5, Safari, and Camino; and in Mozilla and Firefox.
