Syn text editor.
I really like this program. It is open source and includes a ftp client which is so very very useful.
I do all my script language coding on this application (if using windows). Its got syntax schemes for most of the languages I'v needed to use it for.
This is just a text editor (you can't draw your HTML content with this program).
PS. When I code PHP I leave my HTML inside the PHP. If I have PHP doing somthing more complicated than normal then I put that code inside a file of php functions and use the include() function to link the function files to my code. Just leaving the easy to follow PHP and HTML (+CSS) in the main document. That way my files dont get too long and I get some nice reusable collections of functions to use.