How to enable or disable an anchor using jQuery?

The app I'm currently working on does it with a CSS style in combination with javascript.

a.disabled { color:gray; }

Then whenever I want to disable a link I call

$('thelink').addClass('disabled');

Then, in the click handler for 'thelink' a tag I always run a check first thing

if ($('thelink').hasClass('disabled')) return;

To prevent an anchor from following the specified href, I would suggest using preventDefault():

// jQuery 1.7+
$(function () {
    $('a.something').on("click", function (e) {
        e.preventDefault();
    });
});

// jQuery < 1.7
$(function () {
    $('a.something').click(function (e) {
        e.preventDefault();
    });

    // or 

    $('a.something').bind("click", function (e) {
        e.preventDefault();
    });
});

See:

http://docs.jquery.com/Events/jQuery.Event#event.preventDefault.28.29

Also see this previous question on SO:

jQuery disable a link

I found an answer that I like much better here

Looks like this:

$(document).ready(function(){
    $("a").click(function () { 
        $(this).fadeTo("fast", .5).removeAttr("href"); 
    });
});

Enabling would involve setting the href attribute

$(document).ready(function(){
    $("a").click(function () { 
        $(this).fadeIn("fast").attr("href", "http://whatever.com/wherever.html"); 
    });
});

This gives you the appearance that the anchor element becomes normal text, and vice versa.