How to display Web Part Maintenance Page in SharePoint
Often your web part page starts behaving strangely or giving you errors due to some buggy script or web part. This sometimes even stops you to open page in edit mode because of Java Script errors.
Don’t worry, there is a very simple way to delete those web parts. Just append ?contents=1 at the end of the URL of respective page and SharePoint will open the Web Part Maintenance Page for it.