Couple of days ago, writing an ASP page enabling users to download attachment generated on the fly, I struggled a bit on a nice "Internet Explorer was not able to open this Internet site. The requested site is either unavailable or cannot be found" error. As I know that GIYVBF (for those of you who are wondering what it is stands for, try this)

First, I checked several times that I used the correct caching expiration and attachment settings without any success. Finally, the only thing I did not find was this :

If, during the generation of your attachment, there is an non-handled error or exception, the attachment genaration will abort and you will get this famous error message. Thus, this is another way of getting the nice error box....In my case, there was some code accessing a database and when it failed it displayed this message.