Hi Friend,
1.Goto this website
http://www.templatemo.com/page/8[
^]
2.Download any of the css file you like and extract it.
3.In that extracted file there will be a .html page,css page and the images used for that css..
4. Copy that folder and paste it in your project file.
5.Right_click on your add reference click existing item there you will find your extracted css folder open it and add all the files.(.html,css,image)..
6.Open the .html page which has been added to your project. Copy the content and paste it in your .aspx page.
that's it.... Very simple . try it and if you have any doubt post it .i will clarify....
All The Best....