// When the user scrolls down 20px from the top of the document, show the button
document.getElementById("mydiv").onscroll = function() {scrollFunction()};

function scrollFunction() {
//document.getElementById("myBtn").style.display = "block";
if (document.getElementById("mydiv").scrollTop > 20 || document.documentElement.scrollTop > 20) {
        document.getElementById("myBtn").style.display = "block";
    } else {
        document.getElementById("myBtn").style.display = "none";
    }
}

// When the user clicks on the button, scroll to the top of the document
function topFunction() {
    document.getElementById("mydiv").scrollTop = 0;
    document.documentElement.scrollTop = 0;
	
	//var cursc = document.getElementById("mydiv").scrollTop();
	
    
	//alert(Math.max(document.documentElement.clientHeight, window.innerHeight || 0));
}

function pgdown(){
	var viewheight = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);
	document.getElementById("mydiv").scrollTop += 5*viewheight/6;
	document.documentElement.scrollTop += 5*viewheight/6;
}

function pgup(){
var viewheight = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);
	document.getElementById("mydiv").scrollTop -= 5*viewheight/6;
	document.documentElement.scrollTop -= 5*viewheight/6;
}

function viewport()
{
var e = window, a = 'inner';
if ( !( 'innerWidth' in window ) )
{
	a = 'client';
	e = document.documentElement || document.body;
}
return { width : e[ a+'Width' ] , height : e[ a+'Height' ] }
}

/*can prevent scrolling?
$(".ToolPage").bind('mousewheel', function(e, d)  
    var t = $(this);
    if (d > 0 && t.scrollTop() === 0) {
        e.preventDefault();
    }
    else {
        if (d < 0 && (t.scrollTop() == t.get(0).scrollHeight - t.innerHeight())) {
            e.preventDefault();
        }
    }
});*/