CSS

body
This font size for the base allows 10em to equal 10px.

CSS hacks

 * taken from CSS Tip: Targeting IE 5.x, 6 and 7 Separately

Conditional comments
&lt;p&gt;&lt;!--[if IE]&gt; According to the conditional comment this is Internet Explorer&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if IE 5]&gt; According to the conditional comment this is Internet Explorer 5&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if IE 5.0]&gt; According to the conditional comment this is Internet Explorer 5.0&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if IE 5.5]&gt; According to the conditional comment this is Internet Explorer 5.5&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if IE 6]&gt; According to the conditional comment this is Internet Explorer 6&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if IE 7]&gt; According to the conditional comment this is Internet Explorer 7&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if gte IE 5]&gt; According to the conditional comment this is Internet Explorer 5 and up&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if lt IE 6]&gt; According to the conditional comment this is Internet Explorer lower than 6&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if lte IE 5.5]&gt; According to the conditional comment this is Internet Explorer lower or equal to 5.5&lt;br /&gt; &lt;![endif]--&gt; &lt;!--[if gt IE 6]&gt; According to the conditional comment this is Internet Explorer greater than 6&lt;br /&gt; &lt;![endif]--&gt; &lt;/p&gt;
 * taken from Conditional comments

max-width
/* firefox */ max-width: 350px;

/* IE */ width: expression(Math.min(parseInt(this.offsetWidth), 350 ) + 'px');

/* usage */ 