How to validate if textbox value is empty in a series of textboxes?

I would personaly use the disabled html attribute.
See this jsFiddle Demo

html

<form>
    <input  type="text" class="jq-textBox" required="required" />
    <input  type="text" class="jq-textBox" disabled="disabled" />
    <input  type="text" class="jq-textBox" disabled="disabled" />
    <input  type="text" class="jq-textBox" disabled="disabled" />
    <input  type="text" class="jq-textBox" disabled="disabled" />
    <input type="submit" />
</form>

(Note the required attribute for HTML5)

jquery

$('input.jq-textBox').on('keyup', function(){
    var next = $(this).next('input.jq-textBox');
    if (next.length) {
        if ($.trim($(this).val()) != '') next.removeAttr('disabled');
        else {
            var nextAll = $(this).nextAll('input.jq-textBox');
            nextAll.attr('disabled', 'disbaled');
            nextAll.val('');
        }
    }
})

Also see nextAll() jquery Method

Edit : If you want to hide the disabled inputs in order to show them only when the previous input is filled, just add this css :

input[disabled] {
    display: none;
}

Demo