[jQuery] Simple jQuery question

[Julesfrog]

Hi!

I'm new here and also pretty bad at writing javascript. I'm using a
snippet of code by Lloyd Irvin (http://agyuku.net/2009/05/back-to-top-
link-using-jquery/) that allows the user to scroll back to the top of
the page by clicking on a fixed button that fades in only when you
begin scrolling down the page. It's a great code and I'm trying to
rewrite it partially so instead of scrolling to the top it scrolls to
a another section of the website.

This is the original snippet of code from Lloyd:
<script>
        jQuery(function() {
                jQuery(this).pngFix();
                jQuery(window).scroll(function() {
                        if(jQuery(this).scrollTop() != 0) {
                                jQuery('#toTop').fadeIn();
                        } else {
                                jQuery('#toTop').fadeOut();
                        }
                });

                jQuery('#toTop').click(function() {
                        jQuery('body,html').animate({scrollTop:0},
800);
                });
        });
</script>

The script works with this div: <div id="toTop">^ Back to Top</div>.

And here's mine, which is the same except that I replaced the "0"
position to "500":

<script>
        jQuery(function() {
                jQuery(this).pngFix();
                jQuery(window).scroll(function() {
                        if(jQuery(this).scrollTop() != 500) {
                                jQuery('#toTop').fadeIn();
                        } else {
                                jQuery('#toTop').fadeOut();
                        }
                });

                jQuery('#toTop').click(function() {
                        jQuery('body,html').animate({scrollTop:500},
800);
                });
        });
</script>

Now my question. At this point, the button disappears only when the
user hit the 500 mark. I would like it to disappear and stay invisible
when the user reaches the 500 mark and anything below. I think it's
got to do with this line: if(jQuery(this).scrollTop() != 500) but I
just don't know the right "wording".

Also, at this point, when the page loads, the button doesn't show
unless you start scrolling down. Is there a way to make it appear when
the page loads?

I think this is all pretty simple stuff for you developers. It's just
too much for me at this point. I would appreciate your input and
advice.

Thanks!