A good WordPress website must be compatible with all popular web-browsers to make it look perfect to all visitors everytime.
There are many online-tools to test cross browser compatibility of any website. One of them is Browser Sandbox.
Visit Browser Sandbox and you will see a page showing popular web browsers with their images and versions.
Suppose you want to test your website compatibility with Firefox then click ‘Run’ button next to Firefox image then follow on screen steps. You may select from various versions of Firefox you want to test. Same step works for other web-browsers too.
Other cross browser compatibility test tools are: Browser Shots, Adobe BrowserLab and Cross-Browser Testing.