If you want something quik and simple ,then use NVU( http://nvu.com/ ) ,if you need some graphics you can use gimp ( http://www.gimp.org/ ).They are both available for both linux and windows.
If you want something advanced then use notepad++ in windows and kate or kwrite in linux ,they all have greate syntax highlighting.
You should never use Microsoft frontpage for making webpages and/or Internet Explorer for testing ,beacause if you use any or both of them ,you`ll end up with a messey code full of garbage.
If you want to be sure that your site`s code is quality code then you can always chek it with NVU`s "built in" w3c validation or you can access the same thing from the w3c website ( http://www.w3.org/ ).If you ingore this ,you could end up with an incompatible site.

