Let’s say you wish to block all URLs that have the PDF. extension. If you write in your robots.txt a line that looks like this: User-agent: Googlebot Disallow: /*.pdf$. The sign “$” from the end basically tells bots that only URLs ending in PDF shouldn’t be crawled while any other URL containing “PDF” should be. I know it might sound complicated, yet the moral of this story is that a simple misused symbol can break your marketing strategy along with your organic traffic. Below you can find a list with the correct robotx.txt wildcard matches and, as long as you keep count of it, you should be on the safe side of website’s traffic.

I've started a fairly new blog, aimed at fairly new bloggers, by a fairly new blogger! I've had another blog up and running for about four months and it's building up quite well, but I've learned a lot from you here, and am looking forward to trying all the ideas that are new to me. You've been so thorough that I can't suggest a 51, but perhaps a 50a - I use Tweetadder with my Twitter accounts; it's a brilliant tool for automating tasks and driving traffic. I won't spam the comment with a link here, but there is one on my blog for anyone who is interested. Thanks again for all those ideas, cheers, Brent

Let’s say that you want to move your blog from a subdirectory URL (yourwebsiterulz.com/blog) to a subdomain (blog.yourwebsiterulz.com). Although Matt Cutts, former Google engineer, said that “they are roughly equivalent and you should basically go with whichever one is easier for you in terms of configuration, your CMSs, all that sort of stuff”, it seems that things are a bit more complicated than that. 
Search engines (especially Google) are unpredictable. No matter how adept you are at using the AdWords keyword planner or how targeted your SEO strategy is, you can never be completely sure which of your blog posts or even your landing pages will perform the best — and which keywords they’ll rank for when they do. You’ve got to hit publish, then wait to see how the results shake out over time (and it can take months for a post to gain, or not gain, the traction you’re looking for).
Yahoo Answers is one of my favorite traffic generation sources when it comes to answer sites. It has been one of my main traffic sources on a niche site for a long time, even after I haven’t used it for months. The main thing is to give your best when answering. If your answers are chosen as the best ones, you will have more respect in the eyes of the visitors so… yes, more of them will come to check out your blog.
Beyond organic and direct traffic, you must understand the difference between all of your traffic sources and how traffic is classified. Most web analytics platforms, like Google Analytics, utilize an algorithm and flow chart based on the referring website or parameters set within the URL that determine the source of traffic. Here is a breakdown of all sources: