Question

For example we have a textbox which is for tags for a blog. What I want is I want to limit number of tags to be limited.
For instance, “web hosting,php,windows8”.
When the user tries to type another one to textbox which he will start with comma, the textbox won’t let him write it.

Answer 1

In your keypress handler, capture the event object and do;

if (event.which == 44 && $(this).val().split(",").length > 2) {
    event.preventDefault();
}

See it in action here; http://jsfiddle.net/5L7mU/