How many times you have seen this error:
Control 'Button2' of type 'Button' must be placed inside a form tag with runat=server. I bet lot of times. This error comes when you place your control outside the form tag. The fix is very easy just go to html view and cut the control code and paste it inside the form tags OR cut the form ending tag and place it after the control tag.
A much better way is to actually see where the form tags end. You can easily see this in Visual Studio by selecting "View" and than "Details". Now you can see where the form tag starts and where it ends. This way you can just drag and drop your controls in the safe area between the form tags.
