For whatever reasons, sometimes programs (such as your browser) may crash — meaning it would stop working and/or freeze up.
Here shown is an example of Adobe Flash plugin that crashed within the Firefox browser causing it to be no longer responding …
You see that frame of the browser is showing “Not Responding”.
What you have to do in this case is to terminate the Firefox browser program. To do this, right-click on an empty spot on the Windows 7 taskbar to bring up the taskbar menu.
Then select “Start Task Manager”.
In the Task Manager, select the program that is not responding and click “End Task”. In our case, it is the Firefox browser…
A dialog will come up asking whether you want to “Close the program” or “Wait for the program to respond”.
Select “Close the program” to force the program to terminate. Note that if you are working on some work that have not been saved (such as a text document), you will lose whatever work that had not been saved previously.
After closing the program, Windows 7 may popup a dialog saying “Windows is checking for a solution to the problem.”…
If you don’t want to wait for this, just click the “Cancel” button. It should be fine to do so.