var nav = document.getElementById('nav_links');
var nav_links = null;
var last = null;

if (nav){
	nav_links = nav.getElementsByTagName('a');
	last = nav_links[0];
	for (var i = 0; i < nav_links.length; i++) {
	    nav_links[i].onclick = function() {
	        this.blur();
			if (last != this) {
			    last.className = "";
			    opacity(last.id+'_cont', 100, 0, 800);
			    this.className = "selected";
			    last = this;
			    document.getElementById(this.id+'_cont').style.display = 'inline';
			    opacity(this.id+'_cont', 0, 100, 800);
			}
	        return false;
	    }
	    nav_links[i].rel = i;
	}
}


function nextNav() {
    if (last.rel < window.arrayJS.length -1) {
        last.className = '';
		opacity(last.id+'_cont', 100, 0, 800);
        nav_links[parseInt(last.rel)+1].className = 'selected';
        last = nav_links[parseInt(last.rel)+1];
	    document.getElementById(last.id+'_cont').style.display = 'inline';
	    opacity(last.id+'_cont', 0, 100, 800);
    }
}

function prevNav() {
    if (last.rel > 0) {
        last.className = '';
		opacity(last.id+'_cont', 100, 0, 800);
        nav_links[parseInt(last.rel)-1].className = 'selected';
        last = nav_links[parseInt(last.rel)-1];
	    document.getElementById(last.id+'_cont').style.display = 'inline';
	    opacity(last.id+'_cont', 0, 100, 800);
    }
}


function opacity(id, opacStart, opacEnd, millisec) {
    //speed for each frame
    var speed = Math.round(millisec / 100);
    var timer = 0;

    //determine the direction for the blending, if start and end are the same nothing happens
    if(opacStart > opacEnd) {
        for(i = opacStart; i >= opacEnd; i--) {
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
            timer++;
        }
    } else if(opacStart < opacEnd) {
        for(i = opacStart; i <= opacEnd; i++)
            {
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
            timer++;
        }
    }
}

//change the opacity for different browsers
function changeOpac(opacity, id) {
    var object = document.getElementById(id).style;
    object.opacity = (opacity / 100);
    object.MozOpacity = (opacity / 100);
    object.KhtmlOpacity = (opacity / 100);
    object.filter = "alpha(opacity=" + opacity + ")";
}