I'm looking at this technique of uploading a file using Ajax:
http://www.sitepoint.com/html5-javascript-file-upload-progress-bar/
I have two questions about it.
It seems to work on my computer using IE9. I was under the impression that it requires IE10+ according to caniuse: http://caniuse.com/#feat=fileapi
What happens to a users computer who doesn't have an up-to-date browser, will it work like a traditional upload field in IE6 for example?
You can upload files with Ajax without Html5 and you don't need the File Api to do that either. The progress event however is a feature of the XMLHTTPRequest v2, so you'll have to handle that differently for older unsupporting browsers or not show progress at all :)
Alternatively you could write your own upload handler that would report how much of the file has been sent, and then just probe it every x seconds to ask how far it has come. I think Telerik does this with their controls for ASP.NET and MVC.