Código HTML:
function mostrar() { contenido = document.getElementById("Password"); atributo = contenido.getAttribute("type"); contenido.setAttribute("type","password") } function ocultar() { contenido = document.getElementById("Password"); atributo = contenido.getAttribute("type"); contenido.setAttribute("type","text") } input type="text" name="Login" id="Login" class="tam" value="Login" style="text-align:center" onClick="limpia(this)" onBlur="verifica(this)" ><BR> <input type="password" name="Password" id="Password" class="tam" value="Password" style="text-align:center" onClick="limpia(this)" onBlur="verifica(this)" > <img src="ojo.jpg" width="20" height="20" border="0" onFocus="mostrar()" onBlur="ocultar()" />