why the menu tab was unaccessible on IE, but works on Chrome?

I have a quick question, for main menu on front page, I add couple of more menu tab, now, I found a strange issue. On Chrome, all the menu tab was accessible, but on IE or Safari, only the first couple of menu tab above the first half of the picture is accessible, but those menu tab below the first part was not accessible. For example: Add more menu tab to main menu, now I have menu like this: Home Train Catalogue About Us -------------------------------------- (this is the invisible separate line of picture ) FAQ 1 Contact Us _ Policy 3 All of those menu tab works on Chrome, but on IE or Safari, only the first three menu tab can be accessed, but the last three menu tab is visible, but not accessible. I believe it has something to do with the CSS or template, but not sure how to fix it, please offer your advice or suggestions. Thanks.