function switchTab(tabID){
	
	var tabs = document.getElementsByClassName('tab') //tab images
	var cats = document.getElementsByClassName('cat')
	var myPageYOffset = this.pageYOffset
	
	//update tab image
	for (t = 0; t <= tabs.length-1; t++){
 		var myID=tabs[t].id.replace("tab_",'')
		var position = tabID.indexOf(myID);
		
		if (position> -1 && (tabs[t].src.indexOf("_on.jpg") < 0)){
			var source = tabs[t].src.replace(".jpg","_on.jpg");
			tabs[t].src=source; 
		}
		
		else if (tabID == myID){
			tabs[t].src=tabs[t].src
		}
		else {
			var source = tabs[t].src.replace("_on.jpg",".jpg");
			tabs[t].src=source;
		}
 	}
	
	//toggle categories
	for (c = 0; c <= cats.length-1; c++){
 		var position = tabID.indexOf(cats[c].id);
		
		if (position> -1){
			cats[c].className='cat';
		} 
		else {
			cats[c].className='cat off';
		}
 	}
 	//this.scrollY = myPageYOffset
 	this.scrollY = 0
	
	
}