"The remote server returned an error: (404) failed to find" when the Write Automatic Updater program appears

After the WIN2003 is configured, the EXE and DLL files can be downloaded while the client is running, but it is always reported that the "remote server returned an error when updating the lib file: (404) Not Found" error, do not understand how this problem will occur, go online to find the following solutions:

The following methods are found to solve the problem:

Add the MIME type to the Web site as follows:

.*
Application/octet-stream

To do this, open IIS on the server, locate the automatically upgraded folder, view the properties, select the HTTP Headers tab, find a MIME mapping option, click File Type, click New Type, add ". *" to the associated extension, add ". *" to the content type. Application/octet-stream ", Setup is complete.

Try again, OK, pass. Problem solving.

Webreq.getresponse (); The remote server returned an exception: (404) Webreq.getresponse () was not found; The remote server returned an error: (404) Not Found
Help: In doing a software automatic upgrade encountered such a problem webreq.getresponse (); The remote server returned an error: (404) Not Found!

Supplementary question: WebRequest Webreq = WebRequest.Create (Updatefileurl);
WebResponse webres = Webreq.getresponse ();
This updatefileurl is a local absolute path, but this updatefileurl is an on-line. exe file, such as Http://news.china.com/update/eu/aa.exe

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I don't have permission.
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You open the browser, enter in the address bar, to see if this exe is downloaded correctly, if not, it is basically server-side configuration problems or Restrictions
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Permissions issues
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Check if the Updatefileurl is a valid path
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Webclient.download
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The path to add HTTP

"The remote server returned an error: (404) failed to find" when the Write Automatic Updater program appears