How do I get firefox to stop blocking and alert me each time about unresponsive scripts?

message: ” Warning: unresponsive script, ....bla,bla,bla, STOP – CONTINUE” ..... unfortunately I’m not yet expert , so I don’t have a clue of what this actually means, where it comes from, how it happens and how to stop it.. could you please help me, it’s slowing down my work enormously