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Uploading Files Faster in Internet Explorer
http://www.vistaarticles.com/articles/103/1/Uploading-Files-Faster-in-Internet-Explorer
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Published on 11/23/2006
 
Describes how Internet Explorer 7 improves how large files upload when you use the HTTP file upload feature. Internet Explorer 7 uses an improved algorithm to perform the upload operation of an HTTP POST request.

Uploading Files Faster in Internet Explorer

Internet Explorer 7 improves the way that large files are uploaded when you use the HTTP file upload feature. In earlier versions of Internet Explorer, an upload operation may take a long time to finish when you upload a file that is larger than one megabyte. Internet Explorer 7 uses an improved algorithm to perform the upload operation of an HTTP POST request.

Details: http://support.microsoft.com/kb/926188/en-us?spid=8722&sid=global