title: How to know where a CSS error occurred in dynamic content or how to stop the script upon CSS error
body: <p>I'm using JavaScript to dynamically generate the GUI of my web app. Firebug and the Firefox Web Developer Tools are brilliant for inspecting the end result, or for stepping through code using breakpoints, but one thing I don't know is how to catch CSS errors when they occur, and therefore where they occur.</p>
  
  <p>For example, if I have an error in my algorithm, the script might set a "width" to -7px, or set a "left" to "NaNpx". This appears immediately in the Web Developer Extension Error Console's "Warnings" list, but there is no way of knowing which element it occurred on (unless I visually see an obvious result of the badly styled element. The Warnings list just shows it as "Error parsing value for 'width'. Declaration dropped. -130px" with a timestamp and the URL.</p>
  
  <p>If a bad declaration occurs in a static CSS file, then the filename and line number are shown, but this is of course not possible with a dynamic situation. So the question is, is it possible to "break" upon a CSS error? This presumably means I want to stop the script so that I can inspect the current situation and watch variable values. There are thousands of lines of code, so I can't easily put some alerts or breakpoints in, because it's hard to know where to start.</p>