Mouseover button issues

OK, I’ve got an issue with my image not showing up. The size changes as I adjust the px height and width, so I know the code is affecting the right area of my site. Am I missing something?

Here’s the css code:

a.blogbutton {
	display: block;
	width: 112px;
	height: 150px;
	text-decoration: none;
	background: url("BlogButton-112x300.png");
	}

a.blogbutton:hover {
	background-position: 0px -150;
	}

Here’s the html:
<a href="#" class="blogbutton"></a>

Any ideas?