I wonder, is it possible to show exceptions or any errors, like "Null pointer exception" in visualforce? For now all errors refresh the page and displaying error on the blank page. I want for my users, if any system error appears, they would not lost input data in the visualforce page. Iknow about but it only for validating. It is not for my case. My page submits for approval many records at once for 20 approvals with different criterias.