I use javascript and css to build a multi-level drop down menu with following markups: <ul> <li>menu item 1</li> <ul> <li><a href="#">sub menu menu item 1</a></li> ................. This markup is generated by a custom JSTL tag <mui:menu .../> which loads menu data from a database. I hope my jsp page can behave like this: if menu data has not changed since last time I visited the page, just use browser's cache otherwise load from database... How can I do it? I don't know much detail about cache mechanism.