Many ppl in this world are still suffering from ancient Web Browser Like IE6.
Web developer suffers to, web noob like me is also suffeering…

Lucky that since IE 5.5 M$ has provided a unique “Conditional Comments” feature.
Here is how it works, in html:

<p>
<!--[if IE]>
This is Internet Explorer<br />
<![endif]-->
<!--[if IE 5]>
this is Internet Explorer 5<br />
<![endif]-->
<!--[if IE 5.0]>
this is Internet Explorer 5.0<br />
<![endif]-->
<!--[if IE 5.5]>
this is Internet Explorer 5.5<br />
<![endif]-->
<!--[if IE 6]>
this is Internet Explorer 6<br />
<![endif]-->
<!--[if IE 7]>
this is Internet Explorer 7<br />
<![endif]-->
<!--[if gte IE 5]>
this is Internet Explorer 5 and up<br />
<![endif]-->
<!--[if lt IE 6]>
this is Internet Explorer lower than 6<br />
<![endif]-->
<!--[if lte IE 5.5]>
this is Internet Explorer lower or equal to 5.5<br />
<![endif]-->
<!--[if gt IE 6]>
this is Internet Explorer greater than 6<br />
<![endif]-->
</p>

Browsers other than IE will totally ignore these since they appear to them as html comments.

Negative condition is also supported:

<![if !IE]>
A beautiful world that IE holds you from...
<![endif]>

If you peek in the wiki source of main page of my site you'll see that I use this to load Google Friend Connect for non-IE readers.

For more info, see Anti IE6 Campaigns