Luckily for writers, the Nielsen Norman Group did a research study in 2006 that uncovered just how readers scan a page online.
What they found is now known as the F-Pattern. Using cameras and infrared emitters hidden in a seemingly ordinary computer, the Neilson Norman Group conducted eye tracking on 232 users. Though the types of content ranged from search engine results pages to product reviews, the way users read stayed the same for the most part.
The name F-Pattern comes from the eye tracking heat maps that showed 3 core components of user reading behavior which roughly form the shape of an F.
1. First users will typically read horizontally across the top of the page from left to right. (One reason why headlines matter so much.)
2. The eye will then move down the page a little bit, again moving horizontally from left to right.
3. As the reader moves down the page their eye path stays to the left in a more vertical line just skimming the first bit of the lines.
Of course there are exceptions to the rule; sometimes the pattern resembles more of an E for those who read more than they scan, and at the opposite end of the spectrum the really quick readers will often make a single horizontal sweep across the top then sweep down vertically making the shape of an L flipped upside down.
The title of the content on the page is extremely important since this is the most likely to get read in its entirety, opening lines of the opening paragraphs should grab attention and contain useful information, and content should always be left aligned including sub-heading and bullet points which are easy to scan.