User Agent: Mozilla/5.0 (Windows NT 6.0; rv:10.0.2) Gecko/20100101 Firefox/10.0.2 Build ID: 20120215223356 Steps to reproduce: I was trying to download a file of size 190MB. Actual results: Firefox know from the very beginning the size of the file. Only part of the file was actually downloaded (65MB). I don't know if the problem was in the website itself, the internet connection or in firefox. Expected results: Firefox should assert a warning whenever the actual size of the downloaded file is smaller than the expected file size.