1 - Open Firefox explore.
2 - Click "Open Menu" on the right-top and click “Options” open “Options” panel.
3 - Click “General” tab.
4 - Delete mystartsearch homepage link and set a new homepage link. Or click "Restore to Default".
5 - Click "OK".
6 - Choose “Manage Search Engines” in the search list.
7 - Choose "mystartsearch" and click "Remove",then click “OK”.
8 - Restart Firefox explore.