The requested URL could not be retrieved

Question

in my organisation downloading is banned.if file size is more than 3 MB.Plz provide me a solution to get rid of this problem.When i tried to download a big file it opens a page like this....
ERROR
The requested URL could not be retrieved

While trying to retrieve the URL:
http://download618.avast.com/iavs4pro/vpsupd.exe

The following error was encountered:

The Download size is too large .

Contact : Administrator

Your cache administrator is root.