Trick 1: Deleting a bad web part
If you have just added a web part to a page and you get the dreaded error page as a result, add ?Contents=1 to the page’s URL.
You can now delete the offending web part.
Trick 2: Getting to web parts when there is no “Edit Page” in Site Actions
Add &ToolPaneView=2 to then end of the URL. This example will let you see the web parts on a list’s NewForm page.