When a web designer builds a web site they should ensure that the web site looks and behaves as expected in a variety of the most common web browsers.

Browser testing is the process of testing a web site not only in different web browsers such as Safari, Firefox and Internet Explorer, but also in different versions of each browser and on different operating systems.

For example, a web site viewed in Internet Explorer 6 running on Windows XP may behave differently to a web site running running on Internet Explorer 7 on Windows XP or Windows Vista.

The aim of browser testing is to ensure that the visitor to the web site will be able to use the site as expected and if certain visual features are not available, that this does not make the site unusable. This is best achieved by building web sites that comply to web standards.