Try to disable hardware acceleration.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

If disabling hardware acceleration works then check if there is an update available for your graphics display driver.

• https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers

Thank you, it would appear to be a problem with the Intel HD 3000 graphics, I have dual graphics on my laptop and changed it to make FF use the nvidia graphics instead and now the mouse hover is working perfectly.

Very weird issue (we are still in phase of exploring/testing it) encountered with the combination in the same page of 2 (or more) images (buttons) + somes very specific combination of css properties : position fixed/absolute + pseudo class hover (just 1 image alone works ok !? 2 images with position relative/none works also ok, etc.). The issue: hover property doesn' work at all or acts weirdly (both effects of none/link & hover are superposed). Never had (except IE6) /have today this issue with any other browser or older versions such as Ff3627. Not sure if it is related with the above issue & solution, but these are indeed weird and unacceptable problems concering the pseudo class 'hover' with XP-Ff10.0.2. We say 'nacceptable' (up to a point where we migh have to apologize & recommend to our clients not to use/update Ff !) as our webpages have been working perfectly well for years with all browsers, including previous Ff versions (of course we check our sites regularily with all types of new versions and browsers and correct our codes if need be, ...but here it's obviously rather unusual and unexpected from a leading browser, sending us back to pre-CSS2 or IE6 nightmarish prehistory !). Concerning this Ff10 'hover' issue, we are still in a testing phase and implementation of possible software solutions on our servers side. The issue is that we have countless similar 'rollover-style' buttons on numerous pages on our sites. Besides telling millions of clients/users they possibly have to go and update on their computers specific hardware pilots is obviously not an option !

Did you check for other elements overlaying the images if hover doesn't work?

You can use Inspect in the right-click context menu to see which element get selected.

Do you have a test page that shows the problem?

Right... it seems more or less related with some overlaying or underlaying effect... in fact our problem was due to a CSS 'transparency' effect applied to a container...

we kind of sorted out our problem, possibly due to some very basic programming unorthodoxy (?) which we overlooked lost in the middle of some rather complex web pages, php & js scripts, as long as it worked in the past, but there might well be a bug as well in Firefox 10 (?)

we built a test page to reproduce the problem here : 2 buttons: test2 1 button (just same code & css): test1 description problem (see test2): pseudo class 'hover' displays, when mouse is over, at the same time the previous 'non-hover' state of the 'hovered' image

What we call 'button' here is an image with a css hover effect The hover effect used here is just a slight enlargement of the buttons (what we use often on our sites for such buttons; we didn't test anything else more complex rollover effects up to now, such as change of image, etc.).

Issue & solution: our buttons with css 'position: fixed' were enclosed in the html code -possibly poor programming- in a non fixed div with a css transparency applied to this div. As soon as we moved our fixed buttons out of this div, or suppressed the transparency, or applied 'positon:relative' to 1 button it was ok (weird, a position:absolute to one button, which still keeps the problem, ..clears the problem on the other button, still with position:fixed, etc. etc.).

We tested also in applying the transparency to 'body': same problem again (but not sure if body is supposed to support any transparency effect in CSS specs ?) playing with z-index of buttons or containers doesn't seem to solve anything

comments: Tested with XP-Firefox10 (not tested with other MS OS). What puzzled us firstly is that this problem, on various web pages, did not occur with any other main browsers up to now, i.e. IE7&8 Chrome Safari Opera older Firefox such as v3627... (tested also on an old Apple OS with Firefox Safari & Opera). But what puzzled us even more secondly is that the problem occurred on pages with several buttons, and NOT when there was just one button !

Transparency css codes used were the old usual: .transp { filter:alpha(opacity=95); -moz-opacity:0.95; -khtml-opacity: 0.95; opacity: 0.95; }

Can be caused by some optimization that isn't working in this case.
Maybe file a bug report on this to see if anything comes up.