i have 3 selectlists

selectlist1 ---> option1,option2,option3 when user selects option2 , other 2 selectlist should show up for option2 only,
selectlist2 ---> male,female
selectlist3 ---> city1,city2,city3.

does anyone has the idea how can i do that ?

This kind of functionality would normally involve AJAX as each selection causes a post back to get the values that are now needed for the next selection controls.
If the data isn't extensive you could get it all on page load, populate list 1 and use javascript/jquery to alter the 2nd/3rd lists as the first one is changed.