Jquery href click - how can I fire up an event?

If you own the HTML code then it might be wise to assign an id to this href. Then your code would look like this:

<a id="sign_up" class="sign_new">Sign up</a>

And jQuery:

$(document).ready(function(){
    $('#sign_up').click(function(){
        alert('Sign new href executed.');
    });
});

If you do not own the HTML then you'd need to change $('#sign_up') to $('a.sign_new'). You might also fire event.stopPropagation() if you have a href in anchor and do not want it handled (AFAIR return false might work as well).

$(document).ready(function(){
    $('#sign_up').click(function(event){
        alert('Sign new href executed.');
        event.stopPropagation();
    });
});

It doesn't because the href value is not sign_up.It is #sign_up. Try like below, You need to add "#" to indicate the id of the href value.

$('a[href="#sign_up"]').click(function(){
  alert('Sign new href executed.'); 
}); 

DEMO: http://jsfiddle.net/pnGbP/