ul li a text-indent not working

Trying to replace text with a background image in CSS - I'm assuming the fact that my list is display:inline could be causing the issue

Does anyone know how to fix this?

#header{
	margin: 0;
	padding: 0;
	height: 85px;
	width: 100%;
	text-indent: -9000px;
}
#header ul {
	margin: 0;
	padding: 0;
	width: 540px;
	list-style: none;
	display: inline;
}
#header ul li {
	margin: 0;
	padding: 0;
	width: 175px;
	height: 40px;
	display: inline;
}
#header ul li a.home{
	width: 92px;
	height: 32px;
	font-size: 33px;
	background: #fff url('../images/sprite.gif') 0px 0px no-repeat;
}
#header ul li a.services{
	width: 105px;
	height: 32px;
	font-size: 33px;
	background: #fff url('../images/sprite.gif') -105px 0px no-repeat;
}
#header ul li a.aboutUs{
	width: 150px;
	height: 32px;
	font-size: 33px;
	background: #fff url('../images/sprite.gif') -255px 0px no-repeat;
}
#header ul li a.contactUs{
	width: 160px;
	height: 32px;
	font-size: 33px;
	background: #fff url('../images/sprite.gif') -410px 0px no-repeat;
}
 
 
==============
 
 
		<div id="header">
			<ul>
				<li><a class="home" href="index.php">Home</a></li>
				<li><a class="services" href="services.php">Services</a></li>
				<li><a class="aboutUs" href="aboutUs.php">About Us</a></li>
				<li><a class="contactUs" href="contactUs.php">Contact Us</a></li>
			</ul>
		</div>

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