Deleting Firefox user.js

Hi,

We try to push a default company homepage link to all our users browser (IE, Chrome & Firefox), but we got a problem on which the proxy port change from 8080 (our proxy port) into port 80 in all of the browsers while we only change the home page section and leave others option into "preserve client setting".

Another problem is when we try to change the 80 port back into 8080 in Firefox, the change can't be permanent, even we close and reopen Firefox, it keeps show port 80.

Any idea how to accomplish this, and any advice how can we push delete the user.js file created by Desktop Central in Firefox default user profile (%AppData%\Mozilla\Firefox\Profiles\xxxxxxx.default\user.js) in all user that effected by this instead to do it directly in users PC manually.

Appreciate any help.

Thank you.