Design issue in asp menu control

Hi all here,

 

I have a doubt,  I created a web project(has 100 aspx and corresponding codebehind pages) with asp menu (8 menus) controls and i used css and javascript on this menu for the onclick event, now some time  the menu takes more time for alignment(i mean not in the correct place on the screen as i expected..) 

I  can't find the exact solution for my issue, someone here  please help me... thanks..