Don't Fixate on Fixed Heights
The concept of "above the fold" refuses to die. And while it definitely retains some value, it is long-since time to rethink the concept when building a website.
The All Mighty Fold
If you're not familiar with the concept or origin of "the fold", know that it relates to newspapers, and keeping your most important stories above the part of the paper where it gets literally 'folded'. The top half, in other words. Makes sense for paper. People may scan the top half of the news (for those few souls who still read an actual 'paper' newpaper, as I do), and never get to the bottom half. I assume studies have proven this out over time, since it's such an accepted truism that I don't even question it.
But what about screens? Aren't they different?
Meet the Non-Foldable Screen
Designers adapated this concept to desktop monitors as they took their talents to the Web. Going off the assumption that everyone had an 800x600 screen, it was decided that the 'digital fold' would be 600 pixels. The maximum height of the average computer screen. In 1998.
And as screens increased in average size, from 1024x768 to 1366x768, that number still held. Maybe it increased to 700 pixels high, but still, a fixed height. But does that make sense anymore? The web is no longer confined to a desktop computer monitor. It's increasingly flexible and fluid, rendered on smartphones small and large, tablets small and large, high-definition 'retina' displays, and laptops from 11 to 17 inches. And desktop monitors themselves are increasingly found at 27-30" in size. How do you assume what the "fold" is for all these different audiences?
The concept of keeping your most important content or headline at its most visible point holds true, regardless of whether its a phone or a desktop. But beyond that, assume nothing about size. The fold moves.
Websites need to be flexible and fluid, not set inside fixed size boxes. Despite the widely-held belief, people don't mind scrolling for additional content. As long as they feel its worth it, they will scroll. Keep the most important headline and action items up top. Pare you site content down to its bare essentials, and put non-essential information on a subpage or further down the page. But don't assume you know where the "fold" is, it will change for everyone.
What About Fixed Height Websites?
Some people try to get around the idea of varying heights by defining a height for the user. For example, they will make their webpages fixed to 700 pixels high. And any content that goes beyond that height is hidden, until the user scrolls within the webpage itself (not with your browser, which has its own scroll bars).
Fixed height web pages suffer from the same problem as the "fold" issues above – what is the height are you assuming? How can you assume any specific height, with all the different devices and screen sizes available?
Fixed height pages also suffer from usability problems. Users can scroll pages with their fingers or mouse scroll wheel, but a fixed height page will sometimes require they manuever towards a second set of scroll bars. Not impossible, of course, but inconvienent and annoying.
Here are some other good articles on this topic:
(this article in some ways contradicts my article, but worth a read)