function preloadImage (imageName, sourceOut, sourceOver) {
	imageOut [imageName] = new Image();
	imageOver[imageName] = new Image();

	imageOut [imageName].src  =  sourceOut;
	imageOver[imageName].src  = sourceOver;
}

function Out (imageName) {
	if (document.images) {
		document[imageName].src = imageOut [imageName].src;
	}
}

function Over (imageName) {
	if (document.images) {
		document[imageName].src = imageOver[imageName].src;
	}
}

if (document.images) {
	imageOut  = new Array;
	imageOver = new Array;

	preloadImage ("tab_home"         , "img/tab_home.gif"      , "img/tab_home_over.gif");
	preloadImage ("tab_services"     , "img/tab_services.gif"  , "img/tab_services_over.gif");
	preloadImage ("tab_start"        , "img/tab_start.gif"     , "img/tab_start_over.gif");
	preloadImage ("tab_portfolio"    , "img/tab_portfolio.gif" , "img/tab_portfolio_over.gif");
	preloadImage ("tab_contact"      , "img/tab_contact.gif"   , "img/tab_contact_over.gif");
}