If the errorPlacement hook is used to add errors to DOM elements outside the form being validated, the error is added when invalid but never removed when valid. Multiple of the same error can be visible at once because the error is never removed before re-validation begins.

take for example this simple form:

<ul id="clientvalidation"></ul>

<form id="myForm">

Name: <input type="textbox" id="Name" />

<input type="submit" value="submit" />

</form>

with this validation:

$("#myForm").validate({

errorElement: "li",

errorPlacement: function(error, element){

error.appendTo($("#clientvalidation"));

},

rules: {

Name: {required: true}

}

messages: {

Name: {required: "Name is required"}

}

});

If you press the submit button multiple times you'll see the error message appear multiple times.