The concept of Conditional Comments was introduced with the release of Internet Explorer 5. It makes it possible for the developer to detect IE browser versions, and thus give the developer an option to load style sheets based on the version information. This way, your application can take full advantage of the advanced features found in newer browsers, while also writing pages that downgrade gracefully in less-capable browsers or display correctly in browsers other than IE.
Conditional comments should be placed in the <head> section of your pages (or Master page) and has the following syntax:
<!--[if lt IE 8]>
<link href="CSS/StylesheetIElt8.css" type="text/css" rel="stylesheet" media="Screen" />
<link href="CSS/StylesheetMenuIElt8.css" type="text/css" rel="Stylesheet" media="screen" />
<![endif]-->
Make sure you load your general stylesheets before the conditional comment to adhere to the cascading rules of CSS.
Conditional comments come if a variety of flavors like:
<!--[if IE]>...<![endif]--> //If Internet Explorer
<!--[if lt IE 8]>...<![endif]--> //if less than Internet Explorer version 8
<!--[if lte IE 7]>...<![endif]--> //if less than or equal Internet Explorer version 7
<!--[if (IE 6)|(IE 7)]>...<![endif]--> //the OR operator
Conditional comments are Microsoft's preferred means of differentiating Cascading Style Sheets (CSS) rules intended for specific versions of Internet Explorer.
NB! If you are using Telerik's RadControls, then be aware that RadAjax does not interpret the IE conditional comments correctly, i.e., <!--[if lt IE 8]>...<![endif]-->. One simple fix to this problem is to set the EnablePageHeadUpdate property of the
ajax control to false. You may read more about this on the
Telerik Watch blog.