There is a Firefox extension called Vacuum Cleaner Selector
It extracts all selectors from all stylesheets on the page you are viewing, then analyzes this page to see which of these selectors is not used. Then the data is saved in the user settings, so when you continue to move around the site, the selectors will be deleted from the list as they arise. Youll end up with a profile that selectors are not used anywhere on the site.
or give Unused Css a try
http://unused-css.com/
from an unused css site:
Latish Sehgal has written a Windows application to find and remove unused CSS classes. I have not tested it, but from the description you must specify the path to your html files and one CSS file. The program will then list the unused CSS selectors. In the screenshot, there seems to be no way to export this list or load a new clean CSS file. It also looks like the service is limited to one CSS file. If you have several files that you want to clean, you must clean them one by one.
Vacuum cleaner selectors - A Firefox extension (for version 1.5 or later) that finds unused CSS selectors. It extracts all selectors from all the stylesheets on the page you are viewing, then analyzes this page to find out which of these selectors is not used. Then the data is saved so that when testing the next pages of the selector can be deleted from the list as they appear. This tool is supposed to cover a whole site, but unfortunately I can make it work. Also, I don’t think you can customize and load a CSS file with styles.
Topstyle is a Windows application that includes many CSS editing tools. I have not tested it much, but it looks like it has the ability to remove unused CSS selectors. This software costs $ 80.
Liquidcity CSS cleaner is a php script that uses regular expressions to check styles of one page. It will tell you about classes that are not available in HTML code. I have not tested this solution.
Deadweight is a CSS coverage tool. Given a set of style sheets and a set of URLs, it determines which selectors are actually used, and lists that can be "safely" removed. This tool is a ruby module and will only work with the rails website. Unused selectors must be manually removed from the CSS file.
Helium CSS is a javascript tool for detecting unused CSS on many pages on a website. First you need to install the javascript file on the page you want to test. Then you must call the helium function to start the cleaning.
UnusedCSS.com is an easy-to-use web application. Enter the website URL and you will get a list of CSS selectors. For each selector, a number indicates how many times the selector is used. This service has several limitations. The @import operator is not supported. You cannot configure and upload a new clean CSS file.
CSSESS is a bookmarklet that helps you find unused CSS selectors on any site. This tool is pretty easy to use, but it won't let you customize and load clean CSS files. It will list only unused CSS files.