I use the Nivio Lightbox on my client's website and when you open it on a monitor (browser) smaller than the lightbox space it throws a second vertical scrolling bar on a browser. Do you have any clue as what's causing it? Here is the screenshot.
The website linked in your image is not available anymore - which would help to investigate what the problem on your website is. I am guessing you are using some kind of wrapper within <body> with height:100%;
I use the Nivio Lightbox on my client's website and when you open it on a monitor (browser) smaller than the lightbox space it throws a second vertical scrolling bar on a browser. Do you have any clue as what's causing it? Here is the screenshot.