IMO, if you are not familiar with xHTML, CSS and Javascript and are trying to learn, I would not suggest using a Web IDE during your first steps. Once you are familiar with code behind web programming, I would then suggest picking up a web IDE to assist you working faster to get your projects done, especially when your projects get larger and more complex. Dreamweaver is a great editor for that effect (just using the code view). Another which was already mentioned was Notepad++ (which I use for quick opening of files). Another that I've not seen mentioned, which is my primary web IDE, is
Aptana. Its a free/open source Web IDE that supports XHTML, CSS, Javascript as well as various popular Javascript libraries.
There have been some slight issues with program sluggishness, however anyone interested should consider checking it out!