var heightGeneral = 0;

function redimensionar(){

    if(heightGeneral>0)
        document.getElementById("div_contenido").style.height = heightGeneral+"px"; 
    else
        document.getElementById("div_contenido").style.height = "496px";
}


// ************************************************************
// Validaciones generales
//     
var nav4 = window.Event ? true : false;

function soloNumeros(evt)
{
    // Espacio = 8, Enter = 13, '0' = 48, '9' = 57
    var key = nav4 ? evt.which : evt.keyCode;
    return (key <= 13 || (key >= 48 && key <= 57));
}

function soloLetras(evt)
{
    // Espacio = 8, Enter = 13, '0' = 48, '9' = 57, 'A' = 65, 'Z' = 90, 'a' = 97, 'z' = 122 
    var key = nav4 ? evt.which : evt.keyCode;
    return (key <= 13 || (key >= 48 && key <= 57) || (key >= 65 && key <= 90) || (key >= 97 && key <= 122)  );
}