;Jquery: animate page down 100px from current screen position

Check out the jQuery.ScrollTo plugin. You can do something like: $(...).scrollTo( '+=100px', 800 );

Check out the sample for everything this plugin can do: http://demos.flesler.com/jquery/scrollTo/

Just change:

scrollTop: $('body').position().top += 100

To this:

scrollTop: $(window).scrollTop() + 100

See demo: http://jsfiddle.net/fpxuC/

$('html,body').animate({
        scrollTop: $(window).position().top += 100
    })

$('html,body').animate({
        scrollTop: '+=100px'
    })

scrollTop: $('body').position().top += 100

scrollTop: $(window).scrollTop() + 100