Found these steps in a forum,
1-add App_GlobalResources folder
2-add Resource.resx in above folder
3-add Cssurl and your string in above Resource.resx
simply change your href to this
<link href="<%$ Resources: Resource , Cssurl %>" rel="stylesheet" type="text/css" />
though this isnt working for me.
giving css.href value in condition solved my problem 🙂