Checksums do not match when I download file over http

Just for the test I did the following:

Downloaded a page from wikipedia via wget on remote server and named the file test.dat. Then I executed md5sum.

I download the file via http and check it back on my home computer. The checksum does not match.

When I download the same file via scp the checksum matches.

When I compare test.dat and test.dat.original in diff viewer I get these kind of differences. http://ift.tt/1D13NRO http://ift.tt/15ZaGG2

When I download the file via 3g ( not using my mobile phone, not my home wifi ) there is no such problem.

Any idea what might be the problem and what to look for ?