My left navigation, does not work the same in Firefox, and IE

I have a left navigation menu <ul><li> style with background images, my menu is not within an iframe, but when i clic开发者_开发知识库k a menu element in firefox , new page comes like i never leaved that page, feels like kinda Ajax used in the page, But when i click the link in the menu in IE7, i can recognize the page refresh, i can see that i leave the page and can i achieve same result in IE,

if i'm correct FF does not refresh the viewport if you are about to visit a new page, only when the page is loaded (there are some delay thresholds), IE does. without ajax or any other desynchronized / selective loading thing you cant achieve the same effect.