Samizdata - 5:42 pm on Apr 28, 2011 (gmt 0)
If you are on an Apache webserver then you would place an .htaccess directive either in the root directory or in each directory where .ogv files are stored. The code (which I have not tested) should be:
AddType video/ogg .ogv
If you are on some other type of webserver I can't help you.