Getting the filesize of a file with the help of javascript

Hey, Im currently making a script and im having the intention of getting it to work on as much hosts as possible. The big problem with this is that some host (mostly free hosts) turn off alot of vital functions that i need to get for example the filesize of a remote file (or anything remote). Now i had the idea to use some javascript ajax requests to a host that does support that stuff so that it`s still availible on alot hosts.. even if they have it turned off. Now i`m just wondering how you guys would go arround a problem like this and if you think the above is a good idea..? btw.. i have the remote filesize stuff with the help of javascript and ajax working so its not a impossible idea.. its probably just a little harder when you need to get remoe (xml) files with net security update.. or even the remote creation of thumbnails. Thanx in favor, Mark.