If you ever used the ASP.NET file upload control you may be have noticed that if you try to upload a file which size exceeds 4MB, the upload fails.
The reason for this is the ASP.NET precaution against denial-of-service attacks which by default limits the size of the requests at 4MB.
However if in your application you need to upload larger files you may increase this limit, by simply modifying the maxRequestLength attribute in your machine.config file.
<httpRuntime ... maxRequestLength="[Your Value]" ... />