I was going to suggest what I have used - Nvu. But after looking at KompoZer I see that it is based on Nvu (which is no longer being developed). So, if it's better than Nvu, then KompoZer should be really good.

One thing to be aware of when testing your pages, make sure you test in both Internet Explorer as compared to other browsers. The last time I rebuilt my own site, I found everything looked exactly the same in every browser EXCEPT Internet Explorer. It was just minor formatting issues that didn't really affect anything in my case. Nvu and now KompoZer are W3C compliant HTML coders, but MS in their infinite 'wisdom' doesn't always follow standards that the rest of the world does. So just make sure everything looks acceptable in IE, for those few folks who still happen to use it (34.6% on my site this past month).

Brian