WP Responsive theme not working correctly in IE

Hi,

can someone please advise me on what to do….

I have built a site using the free responsive wordpress theme. It all looks how I want it to in safari and chrome on my mac but on Internet Explorer on a PC it has a dark blue rollover on the main navigation for some reason. I have gone into the style sheet and search and replaces all the blue colour codes with white but it hasn’t changed anything when i go back into Internet Explorer. Any ideas? the site is https://www.potnotch.co.uk

Jen