Why is Jquery linking this websit has the different effects with chrome addClass ，ff from IE7？

the problem is Why Jquery linking this websit has the different effects with chrome addClass ，ff from IE7, the website is (http://static.ge开发者_如何学Cewax.org/checktree/index.html). With the Brower Chrome/FF,we can get the normal effect ,get we want,but with the IE7,the effect is different,the checkbox image is disappear,why? The website achieve the checktree. we can get jquery-1.2.6.min.js,checktree.css and jquery.checktree.js from the websit source code. My problem is how can I get the effect with IE7 as the same as with chrome/ff? Thanks

Add this style to your page and you should see the same layout in IE7.

ul.tree li { clear: left; }