Codeigniter based project brower compatibility issues/speed

We have a codeigniter based website, and a bidder must be very familiar with its structure and expertise in programming. We dislike bad coding more than anything else. The problem we have encountered in a web-browser compatibility. For instance, drop-down menus at homepage do not work properly if IE is used while they work fine if used Chrome or Firefox. Also, some of graphics in a page does not show up if IE is used. We need you to test all browsers, IE, firefox, chrome and safari. Find problems and fix them, and make sure all pages are working properly. Also, if you can optimize the loading speed, let us know as well. When bid, please provide your experience and expertise on codeigniter. See the name of the website for this project via attached file. Thanks.