What are the top website-ranking sites? Among the better known sites are Alexa.com and QuantCast.com. Compete.com offers some useful tools as well, and Google itself recently unveiled Google Trends for Websites. Those are all good places to start if you’re looking for a little insight into your competitors’ traffic.

So, how reliable are these sites’ ranking tools? Well that all depends on what you’re relying on them for. If you want specific numbers – as in how many visitors a specific entertainment website (i.e.: JibJab.com) got in June, 2008 – then you’re out of luck. I mean, you may not realize it, but even your own website analytics program doesn’t give infallible numbers. Even if you ran two analytics programs on your own site at the same time, you might not get the exact same numbers from both programs. So, you can imagine that these ‘external’ ranking sites might not be 100% spot-on. After all, they’re tracking and reporting only a fraction of the internet’s traffic (albeit in Google’s case, a large fraction). Alexa, for example, relies on users of its downloadable browser toolbar to unknowingly (ok, sometimes knowingly) report data back about their browsing habits. So, none of these tools are totally comprehensive. Also, smaller websites are generally not tracked at all. If you’re looking for website traffic trends, the more popular the website, the more accurate the data will be.

That’s what you shouldn’t rely on these sites for…but what can you get from them? Well, at the very least you can see trends, you can see big spikes, and you can see big dips in website traffic. And the more ranking tools you see these indicators on, the more reliable the information may be. All 4 sites I’ve listed give much more information than just traffic trends, but that’s the bit we’ll talk about here.

Let’s use the example from above. JibJab.com recently released a new viral political parody video, which has been circulating around the internet. I must have received it a half dozen times from different people. So, I assume their site traffic has jumped because of it. But let’s see if that’s the case…and let’s see if we can get some agreement among the various ranking sites.

Alexa.com: You can see this chart supports my case that something big happened at JibJab recently. The spike in the chart line coincides with the releast of their new video. Up until that point there looks like there was an overall gradual decrease in site traffic.

QuantCast.com: Looks like they’re showing the same spike Alexa shows. But QuantCast actually attempts to quantify the traffic by giving numbers for this particular ‘event.’ According to this chart JibJab’s traffic jumped nearly 5 times from 771k visitors to 3.7Million visitors in just a few days. A big difference between Alexa and QuantCast charts seems to be the rate of decline in traffic from the beginning of the year – but the slope is visually exaggerated here because the QuantCast chart is not as wide as the Alexa chart.

Compete.com: You can see right off the bat that there is no major spike at the end of the Compete.com chart. This is due to the fact that Compete.com’s chart ends in June. So, immediately you can rule them out for identifying any recent trends on JibJab. However, you can see the gradual decline from February ’08 to June ’08, which does agree with the charts above.

Google Trends for Websites: Like Compete.com, Google Trends’ default chart timeline is the past 12 months…but the current month is not displayed…meaning you won’t see any hot trends on this chart, only past trends. It’s clear that the December ’07 spike you see on Compete.com also appears on Google Trends’ chart.

Overall you can see that these ranking tools can be useful for analyzing past site traffic and trends, but they don’t all mirror each other 100%. When using one of these sites, it’s best to check the data against other sources – assuming were really using the data for competitive analysis (and not just to satisfy our voyeuristic curiosity).