is there an extension for dreamweaver cs5 that can support debugging?
I know there are other IDE's like netbeans that can accomplish that task, but I also do html/js and netbeans isn't particularly good for that.
I beg to differ. Those IDEs are, in fact, way better at anything regarding HTML/CSS/JavaScript.
I strongly recommend Zend Studio ($299) or Eclipse PDT (free). NetBeans is supposed to be an excellent IDE as well (just that I'm not familiar with it).
Also, I use Firebug to debug my JavaScripts. It's amazing. Actually, many modern browsers come equipped with JavaScript debugging tools, surprisingly including Internet Explorer (I think only version 8 and above but IE7 might have it too...I don't remember).
I highly recommend Aptana Studio http://aptana.com/ I am using it for along long time and it helped me alot also use google chrome debugger by clicking F12 it is the best html/js debugger
I recommend you to use TSW WebCoder
In TSW WebCoder go to the Debug menu and select Setup debugging. You will be presented with a wizard, which will walk you though the entire process of setting up debugging on your machine.