Common sources of unterminated string literal [duplicate]

I am trying to debug a JavaScript script that gets read in a Firefox extension and executed. I only can see errors via the Firebug console (my code is invisible to Firebug), and it's reporting a "unterminated string literal."

I checked the line and the lines around it and everything seems fine-parentheses, braces, and quotes are balanced, etc. What are other possible causes that I should be looking for?

Most browsers seem to have problems with code like this:

var foo = "</script>";

In Firefox, Opera and IE8 this results in an unterminated string literal error. Can be pretty nasty when serializing html code which includes scripts.

Look for linebreaks! Those are often the cause.