<system.web>
<httpRuntime maxRequestLength="2500000" />
</system.web>
Changing the File Size limit in Web.config for FileUpload control
The default file size limit for the FileUpload control in ASP.Net is 4Mb.
To get around this, in the httpRuntimesection of your website Web.config file, you can set the 'maxRequestLength' (in kilobyte):