Html tag missing

I’m developing a friends site and am using DW CS4 to construct it. So far I have competed most of my pages and decided to upload it to my server to make sure it all works when previewed live. So far I’ve tested the site on 3 different browsers, Internet Explorer 8, Fire Fox 3 & Safari 4, all 3 seem to be doing the same thing.

The problem I’m experiencing is that once you open the [COLOR=“Blue”]website[/COLOR] and try clicking on TESTIMONIALS, the page returns with an error. If you check the url, you will notice that the page is trying to load without the .html tag. Now if you click on the HOME link and then cycle through the other links, the site works as expected.

I’m totally confused, any suggestions?