Web Developers Practically Have Unlimited Open Resources Available
One such tool--Kompozer--allows developers to edit Cascading Style Sheets (CSS) using an easy-to-use CSS editor that features some top notch WYSIWYG features. No HTML skills are required, and Windows, Mac and Linux versions are available.
Quanta Plus, another free tool, is an open source development environment that is popular with PHP developers. It's based on KDE, which has a large following in the Linux community. It enables developers to work on more than one page at a time, and features a full-featured PHP debugger.