• Put critical content at the top of the page, so no one has to scroll down just to find out what the page is about. Don't make me guess what's there.  That overburdens my poor brain.
• At middle levels of content, keep the page content to one or two screen’s worth.
• At higher levels, allow longer pages full of links, if necessary, to give people an overview of the section or site. Scrolling through a huge hierarchy of links turns out to be preferable to jumping down, down, down through multiple menus.
• At lower levels, where users may print the content, allow much longer pages, or divide the content into a series of shorter pages, but offer a printer-friendly button for the whole article.
• Work with designers to avoid horizontal scrolling.

There is evidence to suggest that readers establish a visual memory for the location of items within a printed text based on their spatial location both on the page and within the document (Rothkopf, 1971; Lovelace and Southall, 1983). This memory is supported by the fixed relationship between an item and its position on a given page. A scrolling facility is therefore liable to weaken these relationships and offers the reader only the relative positional cues that an item has with its immediate neighbors.—Dillon (1994)

Only 10% of users scroll beyond the information that is visible on the screen when a page comes up. All critical content and navigation options should be on the top part of the page. —Nielsen (1996)

More users are willing to scroll now. I still recommend minimizing scrolling on navigation pages, but it is no longer an absolute ban. —Nielsen (1997d)

Many participants want a Web page to fit on one screen. —Morkes & Nielsen (1997).

One to three pages of information seems about right for a discreet chunk of information on the Web. A link that produces only a small paragraph of information would be silly in most situations. Very long Web pages tend to be disorienting, because they require the user to scroll long distances, and to remember the organization of things that have scrolled offscreen. —Lynch & Horton (1999)

The top four inches of your Web home page is the most crucial area in your site—because that’s the only area you can be sure most users will see when they hit your home page. —Lynch & Horton (1999)

• For presentations that must grab people’s attention to be successful, don’t make the page longer than the window.
• If you need to present short, clearly segmented chunks of information, you should try to keep your pages short so people won’t miss things that fall off the end of the page.
• If your pages present text that people will want to read at length, it’s all right to use longer, scrolling pages.

As a general rule of thumb, try to make the majority of your pages no longer than one-and-a-half screenfuls of text, and you will probably not get into too much trouble.
—Levine (1997)

Avoid requiring users to scroll in order to determine page contents. Users should be able to recognize immediately whether the subject of any given page interests them.—  (1999)

Most navigation pages should not scroll. However, a scrolling page should be used to contain a long list of navigation links that form a conceptual unit (for example, NFL team links). …

Content pages should contain one conceptual unit of content. In general, people prefer to scroll to continue a single unit of content like an article, skit, or short story, rather than click from page to page of an article. …

Break text in mid-sentence and/or use visual design cues to keep people reading past ‘visual cliffs" or "below the fold".

—Microsoft (2000)

Destination pages that mainly present content and have few navigation options are less harmed by scrolling than navigation pages. After a user has reached a destination page, studies show that he or she will scroll through a few screenfuls if the first screen seems promising. Users will almost never scroll through very long pages, though.

If you have a long article, then the best advice is to rewrite it and make it shorter, or to chunk it into smaller hypertext pages. If you do need to keep a linear structure for some reason, it is better to give in and show the entire article onone page. Even though users don’t like to scroll, they like even less to have to wait for the next page to download while they are in the middle of reading a story.—Nielsen (1999f)

Vertical scrolling is a great way to get around the problem of a small screen, but usability experts have long known that excessive scrolling can disorient computer users. Information that has scrolled off the screen is invisible, and therefore harder to remember. … Many readers may not bother to scroll down to see the bottom of the page. —Lynch (2000)

See bibliography: Black & Elder (1997), Dillon (1994), IBM (1999), Farkas and Farkas (2000), Levine (1997), Lovelace and Southall (1983), Lynch (2000), Microsoft (2000), Nielsen (1997a, 1999f), Rothkopf (1971)