Before you launch your site, or before you implement major revisions to it, test it thoroughly.  Make sure every link works and that every page comes up.  Check it and recheck it.  Having a potential customer encounter busted links or other glitches on your site does not project the image of professionalism you want.

Furthermore, test your site with different browsers.  HTML does not render the same way in every browser.  Not everyone on the web uses the most current version of Internet Explorer, so make sure your site works properly with earlier versions.  For that matter, not everyone uses Internet Explorer so validate your web pages with other popular browsers such as Mozilla Firefox.  A site that looks great on IE may be a total diasaster on Firefox or AOL.

If you are running ASP or PHP scripts, the testing phase is even more important.  You don't want your visitors to be in the middle of a signup, purchase or other activity only to get a script error in the middle of the process.  People usually don't return to sites with errors such as these. 

TEST, TEST, TEST!
 

Following these simple suggestions will help you have a better web site.  Hopefully, having a better web site will lead to more sales!