in page2 when I click browser back button I am coming to Page1 but 3dropwdown values and gridvies is shwoing empty, its not saving the previous selected value.

Hi,
I have page 1 and page 2, In page1 have 3 drop downs and gridview,next button, when I select values in dropdown data is binding into gridview, when I click next buton in page1 I am moving to page2. 
in page2 when I click browser back button I am coming to Page1 but 3dropwdown values and gridvies is shwoing empty, its not saving the previous selected value.
Please help.