Don't roll out your new site until you've tested it vigorously. Here are a few things to check.
Make sure the systems work. Visit the pages, follow the links, fill in the forms, order merchandise, send email. Makes sure the scripts work.
Make sure the systems work with all manner of browsers. Check your site with new and old versions of Netscape Navigator and Internet Explorer. Sometimes a page will show up just fine using one browser and be totally invisible with the other. Check the site using a Macintosh. Check the site using AOL.
Make sure your site meets your design specifications with low bandwidth connections. I like using AOL for this.
Make sure your site looks OK for visitors with a limited color palette. A laptop with an LCD display and 256 color palette is a good tester here.
Get some of your potential visitors to check out the site and try things. Then listen to what they tell you.