<!-- Begin Scripts -->
var ServicesBtnOff  = new Image();
var ServicesBtnOn   = new Image();
var ForSaleBtnOff   = new Image();
var ForSaleBtnOn    = new Image();
var GalleryBtnOff   = new Image();
var GalleryBtnOn    = new Image();
var PatternsBtnOff  = new Image();
var PatternsBtnOn   = new Image();
var TutorialsBtnOff = new Image();
var TutorialsBtnOn  = new Image();
var FAQBtnOff       = new Image();
var FAQBtnOn        = new Image();

function preloadImages()
{
	if (document.images)
	{
	    ServicesBtnOff.src  = "images/ServicesBtnOff.jpg";
	    ServicesBtnOn.src   = "images/ServicesBtnOn.jpg";
            ForSaleBtnOff.src   = "images/ForSaleBtnOff.jpg";
	    ForSaleBtnOn.src    = "images/ForSaleBtnOn.jpg";
	    GalleryBtnOff.src   = "images/GalleryBtnOff.jpg";
	    GalleryBtnOn.src    = "images/GalleryBtnOn.jpg";
	    PatternsBtnOff.src  = "images/PatternsBtnOff.jpg";
	    PatternsBtnOn.src   = "images/PatternsBtnOn.jpg";
	    TutorialsBtnOff.src = "images/TutorialsBtnOff.jpg";
	    TutorialsBtnOn.src  = "images/TutorialsBtnOn.jpg";
	    FAQBtnOff.src       = "images/FAQBtnOff.jpg";
	    FAQBtnOn.src        = "images/FAQBtnOn.jpg";
	}
}

function showBtnOn(which)
{
	if (document.images)
	{
		if (1 == which)      document.ServicesBtn.src  = ServicesBtnOn.src;
		else if (2 == which) document.GalleryBtn.src   = GalleryBtnOn.src;
		else if (3 == which) document.PatternsBtn.src  = PatternsBtnOn.src;
		else if (4 == which) document.TutorialsBtn.src = TutorialsBtnOn.src;		
		else if (5 == which) document.FAQBtn.src       = FAQBtnOn.src;
		else if (6 == which) document.ForSaleBtn.src   = ForSaleBtnOn.src;				
	}
}

function showBtnOff(which)
{
	if (document.images)
	{
		if (1 == which)      document.ServicesBtn.src  = ServicesBtnOff.src;
		else if (2 == which) document.GalleryBtn.src   = GalleryBtnOff.src;
		else if (3 == which) document.PatternsBtn.src  = PatternsBtnOff.src;
		else if (4 == which) document.TutorialsBtn.src = TutorialsBtnOff.src;		
		else if (5 == which) document.FAQBtn.src       = FAQBtnOff.src;
		else if (6 == which) document.ForSaleBtn.src   = ForSaleBtnOff.src;
	}
}
<!-- End Scripts -->