This is in fact a scripting error.  It doesn't have anything to do with
the scroll bar, though.  I have my resolution at 1066x1200 which
provides ample room for the page to render and the scrollbar is never
invoked.

At any rate, I have seen this error before with my own scripts.  In
essence, this is what happens

   1. Mouse hovers over specified area and triggers onmouseover event
   2. onmouseover event calls a function that places a new image at the
      mouse cursor
   3. The mouse cursor is now over the new image so onmouseout is
      triggered from the original image
   4. onmouseout removes the new image
   5. The mouse cursor is now over the original image again, triggering
      onmouseover
   6. Go to step 2

This looping is what causes the flickering image.  If you are the
developer of the page, I would suggest you look into one of these solutions:

    * When the new hovering image is created, its absolute position
      should be such that it does not appear under the mouse cursor
    * When the new hovering image receives focus, a variable is set and
      unset when focus is lost. onmouseout on the original image should
      check to see if this variable is set before removing the original
      image

If you are not the developer, feel free to forward this message to
whoever is.  Hope this helps.

Dustin C. Hatch
http://www.dchweb.com



Harm Geerts wrote:
> On Monday 30 April 2007, Peter Humphrey wrote:
>   
>> Quite often, when I'm viewing a Web page that uses Javascript to overlay a
>> picture with enlarged sections of itself, I find a very rapid flickering of
>> the overlaid section alternating with the background picture. Here's an
>> example: http://heritage.stsci.edu/2007/16/supplemental.html. Does anyone
>> else find this? About Firefox says: Mozilla/5.0 (X11; U; Linux x86_64;
>> en-GB; rv:1.8.1.3) Gecko/20070411 Firefox/2.0.0.3.
>>     
>
> That's a scripting error, when you see the enlargement on mouseover the height 
> of the page increases. The increase causes the loss of the mouseover event en 
> then the page restores to it's original height.
>
> If you increase the size of the browserwindow/desktop so that the enlarged 
> picture doesn't cause the page to scroll the javascript function works fine.
>