I am using the following script for a smooth scroll effect on my single page website: 

```
$('a').click(function(){
$('html, body').animate({
    scrollTop: $( $.attr(this, 'href') ).offset().top
    }, 500);
    return false;
});

```

How can i integrate a minus 100px offset into this script? Sorry im a jQuery Newbie... Thanks for your help and best regards.