Object reference not set to an instance of an object. ?

Somewhere in your code, you are trying to use a variable which contain null as if it contained an actual value, by accessing it's properties or methods. While it is possible to "hide" the problem as you mentioned by using try...catch blocks effectively, it is as Tadit and Ian have said a bad idea.

When you code meets a null variable in that way, it throws an exception and execution of your code stops, and goes to a handler (if any - if none, then you get a message just like you do now). Hiding the message just means that whatever code you wrote to do sotheing with your page will not be executed, and there is no way to make it be executed other than to fix the error properly.

Look at teh error message: it will tell you a file and the line number in teh file that caused the problem. Look at it, and see which variable could be null. If you can't spot it, then we need to see the relevant code fragment that causes the error - not the whole file, just the line and say ten or twenty lines each side, maybe the whole method.