function menuScrolldown(objectName,contentsDivId,offsetX,offsetY, animPixels, animMillisec){

	// requiere un div con el contenido a mostrar. Debe tener definido su ancho y alto en el estilo.

	this.objectName = objectName;

	this.newDivId = "menuScrolldown_"+contentsDivId;

	this.contentsDiv = (document.all)? document.all[contentsDivId] : document.getElementById(contentsDivId);

	this.contents = this.contentsDiv.innerHTML;

	this.offsetX = offsetX;

	this.offsetY = offsetY + ((document.all)? 2 : 0);

	this.height = parseInt(this.contentsDiv.style.height);

	this.width = parseInt(this.contentsDiv.style.width);

	this.timeout = null;

	this.animPixels = animPixels;

	this.animMillisec = animMillisec;

	this.contentsDiv.innerHTML = '';

	document.write('<div style="position:absolute; left:'+ this.offsetX +'px; top:'+ this.offsetY +'px; height:'+ this.height +'px; width;'+ this.width +'px; clip:rect(0,'+ this.width +', '+ this.height +',0)"><div id="'+ this.newDivId +'" style="position:absolute; width:'+ this.contentsDiv.style.width +'; top:-'+ this.height +'" onmouseover="'+ this.objectName +'.desplegar()" onmouseout="'+ this.objectName +'.ocultar()">'+ this.contents +'</div></div>');

	this.divObj = (document.all)? document.all[this.newDivId] : document.getElementById(this.newDivId);

}

menuScrolldown.prototype.mover = function(yFinal,pxStep){

	if(parseInt(this.divObj.style.top) != yFinal){	

		this.divObj.style.top = parseInt(this.divObj.style.top) + pxStep;

		this.timeout = setTimeout(this.objectName+'.mover('+yFinal+','+pxStep+')',this.animMillisec);

	}

}

menuScrolldown.prototype.desplegar = function(){

	clearTimeout(this.timeout);

	this.timeout = setTimeout(this.objectName+'.mover(0,'+this.animPixels+')',this.animMillisec);

}

menuScrolldown.prototype.ocultar = function(){

	clearTimeout(this.timeout);

	this.timeout = setTimeout(this.objectName+'.mover(-'+ this.height +',-'+this.animPixels+')',this.animMillisec);

}