This is not a true statement about mojoPortal.
In ASP.NET, IsPostBack is true for a POST request (i.e form submission) and false for a GET request.
There is no way that I know of to make it behave any different. As far as I know it it not possible to make IsPostBack true on every request and certainly this is not the case in mojoPortal.
This question should have been posted in the developer forum. It is definitely not a bug in mojoPortal.
Best,
Joe