[Excavator]

Hello eetec,
A single line of text is easy to vertically centered with line-height, like this -

.topmenumiddle {
	width: 393px;
	line-height: 41px;
	float: left;
	position: relative;
	/*vertical-align: middle;*/
	color: #fff;
	background: url(../images/top_small_menu_middle.png) repeat-x 0 0;
}

vertical-align
line-height

It gets more complicated if you want to center a paragraph or div element. See some vertical center examples here.
My favorite is the last one which uses a float and a clear.