Why is the slider jumping?

Question

JavaScript

In Firefox, when hovering through the menu, the slider starts jumping, in Chrome there is no such thing. I crawled through the files, I can not understand why.
HTTP://rezplitka.ru/

Answer 1

Something to do with fonts

Answer 2

As a temporary solution until menu refactoring)

/* при ховере добавляеться padding-bottom: 2px и есть небольшие скачки */
#top-menu .tm-inner ul.first-level li.first-level-item {padding-bottom: 0 !important}
.main-slider {clear: left}