function apri(uri,nome,mnbar,tlbar,lcbar,drbar,stbar,scbar,rsz,wdt,hgt) {
window.open(uri,nome,"menubar=" + mnbar + ",toolbar=" + tlbar + ",location=" + lcbar + ",directories=" + drbar + ",status=" + stbar + ",scrollbars=" + scbar + ",resizable=" + rsz + ",width=" + wdt + ",height=" + hgt);
}


<input type="text" name="n" value="Your message" onFocus="if(this.value=='Your message')this.value='';">