<div class="form-group">
    <label for=""><i>Descripción (600 carácteres máx.)</i></label>
    <textarea class="form-control" name="Descripcion" id="descripcion" maxlength="600"  rows="5" required></textarea>
    <textarea class="form-control" name="DescripcionLimpia" id="descripcion_limpia" maxlength="600"  rows="5" novalidate></textarea>

</div>

$("body").on("submit", "#myForm", function(evt)
{

    // Disable things that we don't want to validate.
    $(["input:hidden, textarea:hidden, select:hidden"]).attr("disabled", true);

    // If HTML5 Validation is available let it run. Otherwise prevent default.
    if (this.el.checkValidity && !this.el.checkValidity()) {
        // Re-enable things that we previously disabled.
        $(["input:hidden, textarea:hidden, select:hidden"]).attr("disabled", false);
        return true;
    }
    evt.preventDefault();

    // Re-enable things that we previously disabled.
    $(["input:hidden, textarea:hidden, select:hidden"]).attr("disabled", false);

    // Whatever other form processing stuff goes here.
});