function over( select ) {

	imgElem = document.getElementById( select );
	imgElem.setAttribute( "src" , "images/bt_" + select + "_over.gif" );
	
}

function out( select ) {
	
	imgElem = document.getElementById( select );
	imgElem.setAttribute( "src" , "images/bt_" + select + ".gif" );
	
}