var scrollInterval = '';
var frequency = 60;
var distance = 10;


function scrollup(){
	scrollInterval = setInterval("scrollthis('up')",frequency);
}

function scrolldown(){
	scrollInterval = setInterval("scrollthis('down')",frequency);
}

function stopscroll(){
	clearInterval(scrollInterval);
	document.getElementById("scroll_up").blur();
	document.getElementById("scroll_down").blur();
}



function scrollthis(direction){
	if(direction=='up'){
		document.getElementById("scroll_down").className = "";
		if(parseInt(document.getElementById("page_html").style.top) + distance > 0){
			document.getElementById("page_html").style.top = '0px';
			document.getElementById("scroll_up").className = "disabled";
			stopscroll();
		}else{
			document.getElementById("scroll_up").className = "";
			document.getElementById("page_html").style.top = (parseInt(document.getElementById("page_html").style.top) + distance) + "px";
		}
	}else if(direction=='down'){
		document.getElementById("scroll_up").className = "";
		var minY = -(document.getElementById("page_html").clientHeight - document.getElementById("scroller").clientHeight);
		if(parseInt(document.getElementById("page_html").style.top) - distance < minY){
			document.getElementById("page_html").style.top = minY+'px';
			document.getElementById("scroll_down").className = "disabled";
			stopscroll();
		}else{
			document.getElementById("scroll_down").className = "";
			document.getElementById("page_html").style.top = (parseInt(document.getElementById("page_html").style.top) - distance) + "px";
		}
	}
}


addLoadEvent(function(){
	document.getElementById("page_html").style.top = "0px";
	
	if(document.getElementById("page_html").clientHeight < document.getElementById("scroller").clientHeight){
		document.getElementById("scroll_buttons").style.display = "none";
	}
	
});