Above The Scroll - Web Design
"Above the Scroll" in the web design world is similar to "above the fold" in the newspaper world. You want the most eye-catching content to show up first, and get the reader to view the rest of the page.
From a blog that I read that was originally posted in 2009, the most common screen resolution was 1024 x 768. So to stay above the fold, your most important content should not be below 768px on the page.
To see where your pages would fall at, I recommend installing the Web Developer toolbar for Firefox. It has the ability to re-size the viewport (the part of the browser that displays the webpage) to the dimensions that you specify. I have one of the settings set to show the width of the monitor (1024 at work, 1200 at home) and the height at 768.