Firstly, I have so far made about $3.50 on adsense over past 3 weeks or so. I’m soooo rich. Strangely this correlates with a drop in diffyqs downloads. However, it can’t possibly be from the ads (that is, my first theory was that with the ads less people hit the download link). But the hit rate dropped as well (though I don’t have very good statistics of that before I installed adsense). The first, and I think the main, reason that the hit rate dropped is that geocities went offline. One of the main sites for free textbooks was on geocities. Though the site has a mirror somewhere else, the majority of hits seemed to have come from the geocities site. I assume it will take some time before things get realigned. Just as a side note, there have been over 3200 unique IPs downloading the notes so far.
I think the other reason the hit rate dropped is that we are well inside the semester, so most people taking university courses that were looking for online notes have already found them. I wonder if there will be a “before finals” spike, and if the traffic will pick up in the beginning of the spring semester as it did in the beginning of the fall semester.
One thing that threw me off last time is that the site appeared on stumbleupon. So the hit rate I saw the few days after installing adsense was actually overinflated. Most people that hit the site with stumbleupon never download the pdf. I suppose that’s understandable. When a random person is presented with the possibility of looking at differential equations, they will quickly run away. The hits that come from either google or some of the textbook listing sites frequently result in downloads. Obviously, people searching for “differential equations” are likely to download a textbook on said topic. The normal day hit rate is nowdays more like 100-200 hits with about 10-20 downloads.
The other interesting observation is that the extra stumbleupon traffic, which occasionally happens and make the traffic spike up up to 10 fold the usual levels, doesn’t result in more clicks on the adsense ads. I assume this is because the ads are targetted. They are tutoring or textbook selling sites generally, so a random person is also less likely to click them.
Just for kicks I played around with pngnq to quantize the pngs appearing on the site. Quantizing things to 256 colors reduces size substantially, and if the picture is not a photograph, the quality reduction is not bad. For example, see the full version and the quantized version. The size of this png went down from 53k to 22k. Quantizing does not always result in smaller files though, so always check. That picture was originally even bigger. The stupidest way to save a png results in a far larger file, I think this one was over 70k originally. So you always want to run optipng on all pngs. That generally results in substantial savings already losslessly. I ran optipng on all .pngs on the entire website and generally got anywhere from 10-50% reduction. I also ran it some time ago through the pngs appearing in the genius docs, so that should slightly reduce the ondisk footprint on genius when installed.
Finally, I’ve discovered the first harware flaws in zareason alto 2550 laptop. The sound is kind of crappy and very low volume. It is very substandard actually. This includes using headphones, so it is not just crappy speakers. There is a small possibility that this is a software issue, but I think it is more likely to be the hardware is kind of crap. The other fault I found is that the case is not well thought out at certain points. When you pick up the laptop in certain ways the plastic sort of snaps as two pieces of plastic slide under each other and then back. That’s kind of distressing, I hope it doesn’t break and that it is just cosmetic. Overall though I’m still satisfied enough that I would buy it again.