I have two VF pages. On click of output link in first VF page it will redirect to second VF page by passing two parameters in URL. The example URL of second page is "https:/**************.visual.force.com/apexXXXXXPageNameXXXX?optId=XXXXXX&accId=XXXXXXX". Now i have some custom validations for the fields on second page on click of custom save button on second page it will show error messages by out put text. now here the URL of page is changed to "https:/**************.visual.force.com/apexXXXXXPageNameXXXX".

The problem is after losing the params in URL if i refresh the page it is throwing null exceptions (i can handle them) but if click on cancel button on second page (it should navigate to first page along with parameter) it is going to first page without any params in URL and the first page is showing empty tables because of the absence of param in URL.

My big question is why the parameters are lost from URL after clicking button on VF page. I know that the parameters are still stored in view state even they are hidden from URL. But i dont want to change the URL after clicking on button.