var scroll_flag=false;
var intervalId;
var scrollduration=0;
var scrollratedefault=6;
var scrollrate=scrollratedefault;

function scrollstart(scroll_type) {
	if(window.frames["main"]!=null) {
		scroll_flag=true;
	
		try {
			window.clearInterval(intervalId);
		}
		catch (e) {}
	
		intervalId=window.setInterval("scroll" + scroll_type + "();", 20);
	}
}

function scrollstop() {
	window.clearInterval(intervalId);
	scrollduration=0;
	scrollrate=scrollratedefault;
}

function scrollup() {
	window.frames["main"].scrollBy(0, -scrollrate);
	if(++scrollduration>10) {increaseScrollRate();}
}

function scrolldown() {
	window.frames["main"].scrollBy(0, scrollrate);
	if(++scrollduration>10) {increaseScrollRate();}
}

function scrollleft() {
	window.frames["main"].scrollBy(-scrollrate, 0);
	if(++scrollduration>10) {increaseScrollRate();}
}

function scrollright() {
	window.frames["main"].scrollBy(scrollrate, 0);
	if(++scrollduration>10) {increaseScrollRate();}
}

function increaseScrollRate() {
	scrollrate*=1.1;
	scrollduration=0;
}