Firstly, make sure you have a valid <!DOCTYPE>
. That's the number 1 reason for browser glitches between different browsers/versions.
If you don't have a doctype declaration at the top of your page, the browser will go into Quirks mode, which will cause you problems.
Give it a valid doctype (best go with <!DOCTYPE html>
). That might cause other issues in the short term, but once you've fixed those it will be much better at working properly cross-browser.
Secondly, does it work in other browsers (Firefox, Chrome, etc)? Modern IE versions are generally standards compliant, so if it works in other browsers it should work in IE10/11. If it works in other browsers and not IE11, then you probably have some IE-specific hacks that were needed for older IE version but don't need to be there for newer versions. Get rid of those.