Logging into Yahoo mail with Firefox gives unresponsive script warning

When you log into Yahoo mail using Firefox, you may experience the following problem:

A script on this page may be busy, or it may have stopped responding...

To solve this problem, we need to increase the default script execution time.

1. Type "about:config" in your Firefox address box. Click the I'll be careful, I promise! button.
2. In the Filter box, type "dom.max_script_run_time". 
3. When the filtered result shows up, double click the entry "dom.max_script_run_time".
4. In the pop up windows, change the default value to 20, or 30.

Reference: http://help.yahoo.com/l/us/yahoo/mail/yahoomail/settings/technical-13.html