function tabnav(t){
	document.getElementById('why').style.display="none";
	document.getElementById('requirements').style.display="none";
	document.getElementById('products').style.display="none";
	document.getElementById('results').style.display="none";
	
	document.getElementById('lwhy').style.background="none";
	document.getElementById('lrequirements').style.background="none";
	document.getElementById('lproducts').style.background="none";
	document.getElementById('lresults').style.background="none";
	
	if (t == 'why'){
	    document.getElementById('why').style.display="";
	    document.getElementById('lwhy').style.background="#fff";
	}
	if (t == 'requirements'){
	    document.getElementById('requirements').style.display="";
	    document.getElementById('lrequirements').style.background="#fff";
	}
	if (t == 'products'){
	    document.getElementById('products').style.display="";
	    document.getElementById('lproducts').style.background="#fff";
	}
	if (t == 'results'){
	    document.getElementById('results').style.display="";
	    document.getElementById('lresults').style.background="#fff";
	}
}