mycustompage.htm?aspxerrorpath= error

I have an asp. app. And everything works fine except for 1 page which always give me this error once I publish it to the website.

Sometimes I will publish again, and problem will go away, but today it's just not willing to go away, it kept showing this in the address field:

http://mysiteaddress/mycustompage.htm?aspxerrorpath=/pages/registration.aspx

the real address is:

http://mysiteaddress/pages/registration.aspx

 I use a site map for my app. But all other pages under the same path work fine, except for this page.

Any suggestions what might be the problem? Thanks a lot!!
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