It's that the scrollbar is invisible against the gray right margin. I can't see it. In Firefox, the scrollbar and the right margin are rendered the same color. I can see the buttons at the ends of the scrollbar and I can see the handle, but the scrollbar itself is invisible.
I usually scroll by screens, using the part of the scrollbar that is now invisible.
I can't see the edge of the scrollbar to tell whether or not the mouse pointer tip is inside the scrollbar. Unless the handle or one of the end buttons is near the pointer, I can't tell if I am on the scrollbar or not.
No, I have not changed the color scheme in the Control Panel / Display settings. It is the standard Windows color scheme. But I am using a high screen resolution.
This isn't something that is going to be changed in the short term. Colors always differ slightly from monitor to monitor, platform to platform. What might look like the same color on your computer doesn't on mine. Additionally, the color of the scrollbar is something that is easily user-customizable. For non-customized window colors, Windows 2000, Windows XP, and Windows Vista all, by default, use different shades of grey for Window toolbars / scrollbars. Web browsers also sometimes choose their own color scheme for scrollbars, as the color of scrollbars can be controlled by CSS in web pages. For example, the color of my FireFox scrollbar looks nothing like the color of my Opera scrollbar. Additionally, default scrollbar/toolbar colors are different across Windows, Linux, and Mac.
Unless the grey border was ditched entirely, or was very vastly different (which would change the overall atmosphere of the page), there's no way to slightly change the shade of grey and suddenly make it perfect for everyone out there.
Since you seem to be the only person with this problem, it wouldn't make sense for me to start playing around with the color of the site, which could then affect lots of other people for the worse.
In Internet Explorer, there is a preference to define your own CSS stylesheet, for which you can set the scrollbar color to your choosing (this would not carry throughout your entire Windows settings). FireFox should have a similar option although I haven't checked.
A quick Google search found this site that lets you design your own toolbar color scheme via a visual interface: http://iconico.com/CSSScrollbar/
Just copy and paste the stylesheet it spits out into your browser settings.
I had changed the color of the scrollbar to fix this,
Microsoft's latest upgrade removed the ability to set the color of the scrollbar, so I am back where I was again. I can't see the edge of the scrollbar on the right side of the screen, because it matches the background.