Javascript Errors (IE and Firefox)

I normally come across some javascript errors during development in firefox , which it bypasses(I mean it allows the script to gothrough). But IE never allow you to go through with these js errors. One them is,

Error in parsing value for property " width " . Declaration Dropped . What's this error??

I had a tough time debugging this.

Suppose If you are changing the width of some property (say 'DIV' or 'table ' ) dynamically through your js, then you have to set it this way ,

... document.getElementById('DIV').style.width=" 20 px";

rather than ,

.. document.getElementById('DIV').style.width="20";

NOTE: Make sure that your width never goes negative . It wont work in IE. It will throw you some js error.