There are a few websites that are on the web that can help you determine if your website is truly compatible with every browser from Safari to Mozilla’s Firefox all the way to Google Chrome.
The First is called “Browser Shots” and basically it runs approx on 50 servers with each running a different browser of your site and sending you a snapshot of it.The second website is well known as you may have seen it in the footer tagged on some websites. It’s called Markup Validation service by W3C