If you are using IIS(Internet Information Services) for hosting your web application, then the default upload file size is 4 MB. To increase it, please copy following code in your web.config.
Maximum request length exceeded
<configuration>
<system.web>
<httpRuntime maxRequestLength="1048576" />
</system.web>
</configuration>
If you are using IIS7 or above version then add following code in your web.config
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="1073741824" />
</requestFiltering>
</security>
</system.webServer>