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++;
			if(i == opacEnd) { showhide(id, 'hide'); }
        }
    } else if(opacStart < opacEnd) {
        showhide(id, 'show');
		for(i = opacStart; i <= opacEnd; i++)
            {
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
            timer++;
        }
    }
}

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 + ")";
}

function showhide(id, sh_toggle) {
	var object = document.getElementById(id).style;
	if(sh_toggle == 'show') { object.visibility = 'visible'; }
	if(sh_toggle == 'hide') { object.visibility = 'hidden'; }

}

function toc_show(instruct) {
	if(instruct == 'hide') { showhide('toc_nav', 'hide'); }
	if(instruct == 'show') { showhide('toc_nav', 'show'); }

}