Maximum request length matters when you want to allow upload/download of large files.

This is one of the major change in IIS7. In previous version the default is 4MB, in IIS7 its 28.6MB. So when you deploy your ASP.NET application you will see that it will work for files larger than 4MB, but will give as soon as you cross the 28MB.

In IIS 7, the attribute has been changed to maxAllowedContentLength and it has to appear in <system.webServer> section (as for all IIS 7 settings). The complete attribute will look something like this…

<system.webServer>
<security >
  <requestFiltering>
    <requestLimits maxAllowedContentLength="3072000000" />
  </requestFiltering>
</security>

…