A "Warning: Unresponsive script" dialog box appears when a page takes too long to load. It's helpful because by stopping the script, you may be able to avoid an unresponsive computer. However, this dialog can be annoying if it comes up on nearly every page you visit. Fortunately, you can stop this dialog to avoid the dialog box forever.
Open your Firefox browser. In the address bar, type "about:config" and press "Enter" on your keyboard. Take note that this may void your warranty if you are not sure about what you're doing. Click "I'll be careful, I promise!"
Type "dom.max_script_run_time" in the filter box at the top of the page. The line with this text should appear on the screen, and all other options should disappear.
Double-click on the "dom.max_script_run_time" text. Change the time that you want Firefox to wait before getting a script error. Set the number to "0" so that no dialog boxes or warnings will appear.
Click "OK." Restart your Firefox browser.
You may change the dom.max_script_run_time to a value above the default (5 to 10 seconds) so that the dialog does not appear so soon. For best results, the value should not be set above 20 seconds.
Do not edit anything else on the about:config page if you do not know what you're doing. This could cause serious errors to your browser and may void your warranty.