I honestly don't know. I started out using frontpage some 5-6 years ago, but decided to learn to code by hand, using nothing but notepad. Something I've never come to regret.
Currently i use either Eclipse or Notepad++, which both supports collapsing of code blocks, as well as tabbed editing and syntax highlighting of code.
I would never recommend anyone to use WYSIWYG tools, because they actually don't increase your productivity like some claim they do. Plus they usually write messy code, either due to improper use, or due to editor limits.
In any case, don't just blindly rely on the editor. You should at least know the standards behind, because the editor can't get everywhere, with its big clumsy fingers. I made a list entitled Web
Designers Tools List Including most of the tools i currently use.
With that many pages, i would start considering using PHP/MySQL. Or finding a CMS solution. I only do static pages when I'm making templates/examples.