Selenium is not able to perform mouseOver if Hover property is defined in CSS
You can try yourself on this link using selenium ide
http://www.w3schools.com/cssref/tryit.asp?filename=trycss_sel_link_more2
Selenium mouse Over has no effect on this link
please visit this link
According to this question, this is one of those perennial problems Selenium and :hover css
They discuss a couple of solutions, but it looks like the problem is that as Javascript cannot trigger the :hover pseudo class, so Selenium can’t either.