[Simon Lloyd]

You really only need to turn strings on and off

For targeting IE Users:
<!--[if IE]>
Place Content here for Users of Internet Explorer.
<![endif]-->

For targeting all others:
<![if !IE]>
Place Content here for Users of all other Browsers.
<![endif]>

The Conditional Comments can only be detected by Internet Explorer, all other Browsers thread it as normal Comments.

To target IE 6,7 etc.. You have to use "Greater Then" or "Lesser Than" in the If Statement. Like this.

Greater Then:
<!--[if gte IE 7]>
Place Content here for Users of Internet Explorer 7 or above.
<![endif]-->

Lesser Then:
<!--[if lt IE 6]>
Place Content here for Users of Internet Explorer 5 or lower.
<![endif]-->

You can do the same for other specific browsers like geko....etc