alt Hacker NewsThis is so funny that I'm not even sure what to say. You can ask your exact questions about a newspaper but somehow 99% of people manage to read them just fine. I think it's just a you problem that you are looking for an exact algorithm on how to scan a page with multiple sizes of content; in reality, people just look over it all and keep track of what they have or haven't looked at all in their heads.
In a newspaper the answer is simple. You linearly scan the leftmost column to the bottom of the page, then the next column, then the next, and so on until you get to the end of the page. At no point do you ever need to keep track of anything other than "this is how far I've gotten" to make sure you haven't missed anything. Columnar layout make sense in newspapers because both axes are fixed in size, so all you ever do is one long linear scan with wraparound.