I ran into an annoying problem: the following code gives a warning in Visual Studio.
I can't believe how many responses say "Put the JavaScript in the code-behind instead". This is a very bad idea, and muddles your code by mixing presentation with business logic. As the original poster stated, this is only a mere warning. While annoying, it's not worth mixing your presenatational behavior in with your server-side code (a.k.a. writing poor code) over.