First, include the jQuery and masked input javascript files.

<script src="jquery.js" type="text/javascript"></script>
<script src="jquery.maskedinput.js" type="text/javascript"></script>

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

jQuery(function($){
   $("#date").mask("99/99/9999",{placeholder:"mm/dd/yyyy"});
   $("#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");
});

You can have part of your mask be optional. Anything listed after '?' within the mask is considered optional user input. The common example for this is phone number + optional extension.

jQuery(function($){
   $("#phone").mask("(999) 999-9999? x99999");
});

If your requirements aren't met by the predefined placeholders, you can always add your own. For example, maybe you need a mask to only allow hexadecimal characters. You can add your own definition for a placeholder, say 'h', like so: $.mask.definitions['h'] = "[A-Fa-f0-9]"; Then you can use that to mask for something like css colors.

jQuery(function($){
   $("#phone").mask("#hhhhhh");
});

By design, this plugin will reject input which doesn't complete the mask. You can bypass this by using a '?' character at the position where you would like to consider input optional. For example, a mask of "(999) 999-9999? x99999" would require only the first 10 digits of a phone number with extension being optional.