Masked Input Plugin

First, include the jQuery and masked input javascript files.

jquery.js
jquery.maskedinput.js

Next, call the mask function for those items you wish to have masked.

jQuery(function($){
$("#date").mask("99/99/9999");
$("#phone").mask("(999) 999-9999");
$("#tin").mask("99-9999999");
$("#ssn").mask("999-99-9999");
});

Optionally, if you are not satisfied with the underscore ('_') character as a placeholder, you may pass an optional argument to the maskedinput method.

jQuery(function($){
$("#product").mask("99/99/9999",{placeholder:" "});
});

Optionally, if you would like to execute a function once the mask has been completed, you can specify that function as an optional argument to the maskedinput method.

jQuery(function($){
$("#product").mask("99/99/9999",{completed:function(){alert("You typed the following: "+this.val());}});
});

You can now supply your own mask definitions.

jQuery(function($){
$.mask.definitions['~']='[+-]';
$("#eyescript").mask("~9.99 ~9.99 999");
});

http://digitalbush.com/projects/masked-input-plugin/