Button Background

Hello,

I wonder if someone can help me I am having some problems with my buttons, for some reason I am unable to stop the background from going black when they are hovered over. I have hunted for days trying to locate where this hover background is coming from if someone could help that would be amazing.

I am unsure how long it takes to reply to these things but potentially my site will have gone live by the time its seen so the URL will be http://www.equii-est.co.uk

The page I need help with: [log in to see the link]