In the past few years, you've likely noticed that a lot of blogs and websites have there content on the left and their ads on their right. Some even go so far to use that sort of two column layout and push their content below the fold and only display ads above the fold.
I never understood why this became popular. Before this, many websites used to have navigation on the left side of their content, and many users still expect to see it there. Google even indicates that the left side of the page does well as illustrated in this heat map they released. The darker the color, the better the performance.
Even on my own sites, testing ad placements, I've found the left side of the page performs very well. Especially for AdSense link units.
But still many people are using and designing templates with ads on the right and I think it has to do with an SEO Myth I've seen many times.
I've seen many SEO "experts" say the same thing "googlebot reads your page from top left to bottom right" or sometimes "top to bottom and left to right". Which can sort of be considered accurate, but then they go on to describe how putting navigation or other less important content to the left of your page will screw up your rankings. This is so wrong.
Googlebot doesn't know how your page is displayed
The most important important content of your site should come first in the HTML code of your page to help search engines understand it's importance. How it's rendered on the page is irrelevant and you should make sure your page displays the best it can for your users and for the best ad performance, then make sure your HTML code is as search engine friendly as it can be. Google has some pretty smart folks working for them and they've spidered many sites so I think that figured out how to handle left nav bars since many big sites use them and still come up in the SERPs.
Back when people were using table layouts, this wasn't as obvious, but if you're using CSS formatting use these tips to improve SEO. There's a learning curve to CSS but it provides a much better experience to your users. If you're still using table based layouts heres a tip to get your content first in your HTML.
In addition to noticing that click through rate and revenue has increased from ads that were moved to the left, the number of pages that a visitor reads also does better when there's easy navigation where the user expects it.
I have some blogs which use the standard two column layout with the ads on the left and also with the ads on the right. The ones I have with three column layouts and navigation on the top left of the content have higher page views per visitor and a lower bounce rate. That's anecdotal and I haven't done any real testing, but I know that when I hit a page from a search engine, if the article I landed on wasn't exactly what I was looking for, I look for quick navigation that might indicate that it might be there before I click the back button.
The SEO Myth may not be the only reason people do this. Some blogs don't have traditional navigation like other types of websites do. At least that's what they believe. Blogger.com is a bit limited because it only gives you labels, but other blog software gives you categories in addition to tags/labels. On this blog, I've decided to treat labels as categories and try to keep them broad and to a minimum. That way I can use them in the left nav bar of this design.