function ancho(porcent) {
		return Math.round(window.screen.availWidth*porcent/100);
	}
	function alto(porcent) {
		return Math.round(window.screen.availHeight*porcent/100);
	}
	
	function openCenteredWindow(path,nombre,longX,longY,scroll,resize,toolbar,status,x,y) {
		var pX,pY;
		try {if (!isNaN(x)) pX=x; else pX = (screen.width-longX)/2;} catch (e) {pX = (screen.width-longX)/2;}
		try {if (!isNaN(y)) pY=y; else pY = ((screen.height-longY)/2)-20;} catch (e) {pY = ((screen.height-longY)/2)-20;}
		try {if (scroll!='no') scroll='yes'} catch (e) {scroll='yes'}
		try {if (resize!='yes') resize='no'} catch (e) {resize='no'}
		try {if (toolbar!='yes') toolbar='no'} catch (e) {toolbar='no'}
		try {if (status!='yes') status='no'} catch (e) {status='no'}
		var ventanuco = window.open(path,nombre,'scrollbars='+scroll+',resizable='+resize+',toolbar='+toolbar+',status='+status+',width='+longX+',height='+longY+',left='+pX+',top='+pY);
		ventanuco.focus();
		return ventanuco;
	}