Notepad is a very good EDITOR if you are going to edit single files and don't need/want syntax higlighting etc
Visual Studio (.Net) is a very good tool for editing complete sites. It
has syntax highlighting(both HTML and ASP), search and replace
functions (single/multiple/all files), pops up suggestions on methods
and tags when you are writing, CSS editor, HTML design editor (

), and everything else you need.. but it is quite expensive if you want a legal copy..
ASP.Net WebMatrix is also a good tool (and free). it's made for
ASP.Net.. it has syntax highlighting for HTML and ASP.Net, but not ASP,
but is better than Notepad. It aslo has a file browser on the left side
and a good HTML design editor..
FrontPage should be avoided at all costs, at least earlier versions
than 2003. I have not tried the newest version, but people has said
it's better on code handling than the others..
Dreamweaver has support for everything and it can auto generate code
for you(please avoid!!), but if you write everything yourself in the
code editor, it's almost as good as VS.Net (I believe) and much cheaper
but if you want a free one, I'm not quite sure.. ASP.Net WebMatrix is the best I can think of..