function showPopup(url, width, height) {
	var centerLeft = (screen.width - width) / 2;
	var centerTop =  (screen.height - height) / 2;
	//Utilizamos una expresión regular en el 2º parámetro del método window.open para eliminar los caracteres no alfanuméricos.
    popup = window.open(url, null, 'width=' + width + ',height=' + height + ',resizable=0,left=' + centerLeft + ',top=' + centerTop); 
	//popup.moveTo(centerLeft, centerTop);
	return popup;
}
function advertiseWithUs() {
	showPopup('http://www.aboutsummercamp.com/internetmarketing/advertisewithus.aspx', 400, 430);
}
function contactUs() {
	showPopup('http://www.aboutsummercamp.com/internetmarketing/contactus.aspx', 390, 330);
}
function linkToUs() {
	showPopup('http://www.aboutsummercamp.com/internetmarketing/linktous.htm', 400, 270);
}
function recommendUs() {
	showPopup('http://www.aboutsummercamp.com/internetmarketing/sendtoafriend.aspx', 400, 270);
}