HTML Code:
.home li a:hover {
background: url("http://www.homeschoolshare.com/blog/wp-content/uploads/smile_hover.png") no-repeat scroll left!important;
}
in english says "when you hover on a link that is part of a list in an HTML element with a class of 'home' use this background.
the only element that gets a class of 'home' is the <body...> element and it is only assigned when you are on the home page. So when you go to another page, the CSS Selector (.home li a:hover) doesn't match anything so the background rule is not applied