conditional usage <!--[if IE 6]>

[earth2mac]

Can I use it in an embeded as well as an external? Which is best practice?

external:
<!--[if IE 6]>
<link rel="stylesheet" type="text/css" href="ie-6.0.css" />
<![endif]-->


embeded:
<!--[if lt IE 7]>
<style>
#footer .search
{
margin-top: -1.6em;
}
</style>
<![endif]-->

[WebJoel]

Both are valid. I tend to leave my CSS 'internal' but advocate making the CSS being an external file.
I mostly 'do' internal CSS for posting purposes so I don't have to cull two code-boxes. I also find 'grabbing' other's code for assistance easier when internal, because if the CSS is 'internal' (before "</head>") and I can lift everything into my HTML-editor faster and run with it..