Aardvark - A cool
extension for web developers and designers, allows them to view CSS
attributes, id, class by highlighting page element individually.
chromEdit - Alter the appearance of any page by editing CSS and Javascript files with this extension.
CSSMate - Firefox extension to edit CSS files.
CSS validator - Check the validity of your webpage using this CSS validator extension.
CSSViewer - See the CSS properties of page elements with this extension.
EditCSS - Play around with loaded CSS, Web Developer extension also provides this functionality.
IE Tab - Designers and developers can view their CSS projects on Internet Explorer using this extension.
Style Sheet Chooser II - Users can pick and choose alternate style sheets for a website.
FireBug - A console for debugging JavaScript, HTML, and Ajax code snippets.
HTML Validator - Cool extension to validate web pages with HTML standards of W3C.
JavaScript Debugger - JavaScript debugging extension enables a strong debugging environment.
PHP editor, Maked to be light, easy and simple,
integrated with PHP by php4delphi component,
Highlight by SynEdit component,
Debuging XDebug.org DBGp protocol,
has internal console for learning php easy, Run, Check, Breakpoints and Watches
PHP is having various functions for debugging a variable. Seeing values stored in an array or in any other object is important for doing any troubleshooting in a code.