As a dearly departed friend used to say, "The only thing about Dreamweaver that can be considered professional grade tools are the people promoting it's use". 90% of what it does is teach you how NOT to build websites, and by the time you don't need that 90%, you're back down to a overglorified notepad replacement and throwing money out the window - like as others have mentioned there are plenty of decent flat text editors that are OVERKILL for something as simple as writing HTML and CSS (or even XML, PHP, mySQL, ASP, PERL, Python, Ruby, C, Pascal or any other programming, scripting or markup language you could name)
My current favorite:
Is nice because of it's line wrapping options, ability to turn of the annoying acid trip of color syntax highlighting, and it NOT being tabbed or restricting everything to one window -- so I can for example have my CSS open in one window at a third of screen width, HTML in another, and then any other code in yet another; then simply alt tab to ALL the browsers for testing... since if you are testing against just one browser, you are more likely to lead yourself down the garden path on a technique that might simply not work everywhere.
But there are plenty of others
Over on the Mac you have Text Wrangler, which if you're on Lion is an easy free install off the App Store.
*nix users get a whole slew of editors of differing complexities, from the easy to use gEdit on Gnome, to the very complex but powerful (and often annoying) vi/vim.
Franky, if you 'need' anything MORE than a flat text editor for making the HTML/CSS for a website, you might want to consider doing something else.
WYSIWYGS are rubbish, the sites they make are rubbish -- in terms of accessibility, maintainability and sustainability they are nothing but unmitigated disasters.