probably my answer was not informative enough: a lot of people search
the web for "ajax progress bar", thinking that they can show the real
progress of a file upload only via javascript. That is wrong, as colin
says, the server needs to support this, and spit out the data for
javascript to use, via, ajax calls.
IF the server does not, the only alternative is to use swf.
serverside tech that allow it are , to my knowledge, PHP 5.2 and Perl.
Probably coldfusion an ASP, but you'll have to check that.
If you need a progress bar for something else than file upload, such
as showing the status of loading several scripts (like google mail
does), then that is indeed pure javascript.
hope this helps clarify my point !
cheers to all,
Alexandre Plennevaux
LAb[au]
http://www.lab-au.com