I've come across this problem before and want to try and document some solutions here.
Today's mishap was a blank page from an ASP.NET MVC application when deployed. It turned out that this was because the Authorization system (in this case Active Directory) had not recognized me so the [Authorize(Roles = "Everyone")] attribute that I'd added to the controller was saying that I wasn't a member of the group Everyone. By removing this attribute and redeploying I confirmed that this was the problem.
Another reason for a blank page is if a generic error is happening but you're handling that generic error and suppressing it. There's an answer here with more info on that type of blank page.