A recent Forrester Research report reported that failure to ensure website quality will cost the average small or mid-size company thousands of dollars in wasted expenditures on website redesigns, forfeited revenue, and lost customers. Testing a website is a long and tedious task, but it's perhaps the most important task of all. There are numerous stages to testing, all of which are very important. Ranging from browser testing to content testing, none should be excluded.

Visual Acceptance Testing Visual Acceptance Testing is the first port-of-call for all webmasters. This type of testing generally ensures that the site looks as it is intended to. This includes checking the graphic integration, and simply confirming that the site looks good. In this stage you should assess every page carefully to ensure that each looks the same. The site should be tested under different screen resolutions and color depths.

Functionality Testing
Functionality testing is perhaps the most vital area of testing, and one which should never be missed. Functionality testing involves an assessment of every aspect of the site where scripting or code is involved, from searching for dead links, to testing forms and scripts.
You should also test your payment processing system completely and thoroughly. After all, you wouldn’t want a potential customer to get stuck at the last stage and eventually leave the site just because there is something wrong with payment processing.

Content Proofing
This stage of testing removes any errors in your content, and ensures that your site has a professional appearance. In this phase, you should reread each page on your site, and check for spelling and grammatical errors.

System and Browser Compatibility Testing
This test phase is completed in order to ensure that your website renders correctly on a user's screen. To begin with, you should test several pages from your site on different browsers such as Internet Explorer 4, 5, 6, Netscape 4 and 6, and Opera. This can be extremely important - if your site does not work properly with the Netscape browser, Netscape users will end up annoyed, and they'll go elsewhere.