Limit WebClient DownloadFile maximum file size

In my asp .net project, my main page receives URL as a parameter I need to download internally and then process it. I know that I can use WebClient’s DownloadFile method however I want to avoid malicious user from giving a url to a huge file, which will unnecessary traffic from my server. In order to avoid this, I’m looking for a solution to set maximum file size that DownloadFile will download.

Why does FireFox 3.6.8 not cache static contents from asp.net developer server?

I am working on a asp.net web site, like normal user, we use asp.net developer server during coding and testing.
Today, I found the firefox not cache any static file of my site, since our application is pretty big, it made page load time very slow.
I checked firefox about:cache, all the static file cache setting looks like