Umbraco 404

Hello everybody
After i added a seperate page that was not at the site, the "link to document" changed from "/" to "frontpage.aspx" for the frontpage and when i enter frontpage.aspx it throws an 404. 
No matter what page i try to visit, it throws an 404 now. An 404 from the server and not from umbraco.
The administration does not throw a 404, that is frustrating me and i dont know why.

Thanks for the help
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