css optimization for all main browsers

I need of a work that assure that a website is exactly the same in all main browsers. Is a simple website in trial mode: [login to view URL] it was developed under firefox on ubuntu ## Deliverables The site is done with wordpress, I will give you ftp access to trial server, with a small explanation of theme file location. Developer will change only [login to view URL] to include different css file if necessary, and [login to view URL] screenshot of all test are required, for examle using [login to view URL]