When I watch hulu on my second monitor the screen does not stay full screen when clicking on my main monitor. Is there a setting I can change to fix that?
Unfortunately this is just one of joys-of-Flash. As soon as it detects it has lost focus, it'll shut back down to regular size.
There are a couple of workarounds that work in the same way:
Both allow you to zoom in on something on the screen and both allow you to do this on one screen without affecting the other. Zoom in on the Flash applet (or game, or whatever) and you're away!