IE Conditional Comments to target specific stylesheet
Microsoft is slow in adding all the new CSS & styling standards to IE. Many of the new CSS3 features will only work in IE versions 9+ while other browsers like Chrome, FireFox, Safari & Opera support many of them now.
Most of the computers(especially in huge companies) are still using IE8 or IE7. If you decide to use some of the new CSS features in the web application, it will not work in IE7 or IE8. Unless it is a critical application used across the company, it will be difficult to convince the IT department to force an upgrade to IE9.
In these environments, one could you use the Condition Comments feature provided by Microsoft from IE5+. You can use these conditional comments to point to a different style sheet to gracefully degrade your application in less capable IE versions.
Conditional Comments Syntax -
<!--[if lt IE 9]>
<link rel="stylesheet" type="text/css" href="iespecificStyle.css" />
<! [endif] -->
Make sure there is no space in the first line till the if statement(marked in bold).
You can read more about the conditional statements in MSDN - http://msdn.microsoft.com/en-us/library/ms537512(v=vs.85).aspx
This is especially useful when you use mediaqueries to target different devices as mediaqueries is only supported from IE9+.