function showBox(box1){
		overlayHeight();
    $('overlay').show();
	$(box1).show();
    center(box1);
    return false;
}

function hideBox(box1, box2){
    $(box1).hide();
    $(box2).hide();
    $('overlay').hide();
    return false;
}

function center(element){
    try{
        element = $(element);
    }catch(e){
        return;
    }

    var my_width  = 0;
    var my_height = 0;

    if ( typeof( window.innerWidth ) == 'number' ){
        my_width  = window.innerWidth;
        my_height = window.innerHeight;
    }else if ( document.documentElement && 
             ( document.documentElement.clientWidth ||
               document.documentElement.clientHeight ) ){
        my_width  = document.documentElement.clientWidth;
        my_height = document.documentElement.clientHeight;
    }
    else if ( document.body && 
            ( document.body.clientWidth || document.body.clientHeight ) ){
        my_width  = document.body.clientWidth;
        my_height = document.body.clientHeight;
    }

    element.style.position = 'absolute';
    element.style.zIndex   = 99;

    var scrollY = 0;

    if ( document.documentElement && document.documentElement.scrollTop ){
        scrollY = document.documentElement.scrollTop;
    }else if ( document.body && document.body.scrollTop ){
        scrollY = document.body.scrollTop;
    }else if ( window.pageYOffset ){
        scrollY = window.pageYOffset;
    }else if ( window.scrollY ){
        scrollY = window.scrollY;
    }

    var elementDimensions = Element.getDimensions(element);

    var setX = ( my_width  - elementDimensions.width  ) / 2;
    var setY = ( my_height - elementDimensions.height ) / 2 + scrollY;

    setX = ( setX < 0 ) ? 0 : setX;
    setY = ( setY < 0 ) ? 0 : setY;

    element.style.left = setX + "px";
    element.style.top  = setY + "px";

    element.style.display  = 'block';
}

function overlayHeight(){

	var bdimensions = $('main_container_id').getDimensions();
	var bheight = (bdimensions.height + 250);
	var winHeight = (typeof window.innerHeight != 'undefined' ? window.innerHeight : document.body.offsetHeight);

	if (bheight > winHeight) 
		{
			$('overlay').setStyle({ height: bheight + 'px' });
		}
	else {
		$('overlay').setStyle({ height: winHeight + 'px' });
	}
}