Hello,
You should to open http://your_site/plugins/content/extravote/assets/extravote.css and change there:
.extravote-star a:hover {
background-position: left bottom !important;
}
to
.extravote-star a:hover {
/* background-position: left bottom !important;*/
}
or add to any css-file of Your template (at the bottom):
.top_extravote_item .extravote-star a:hover {
background-position: none;
}