The browser and the corresponding developer tools

 

1. Firefox

plug-in : Firebug ( http://getfirebug.com );

2. Chrome

Chrome Developer Tools ( https://developers.google.com/chrome-developer-tools/ );

3. Safari

Safari Web Inspector ( http://developer.apple.com/technologies/safari/developer-tools.html );

4. Internet Explorer 
Internet Explorer Developer Tools ( http://msdn.microsoft.com/en-us/library/dd565628.aspx );

5. Opera

Opera Dragonfly ( http://www.opera.com/dragonfly/ )