SEO Problem: Uppercase vs Lowercase URLs
From my experience, this problem is most common on websites that use .NET. The problem stems from the fact that the server is configured to respond to URLs with uppercase letters and not to redirect or rewrite to the lowercase version.

I will admit that recently, this problem hasn't been as common as it was because generally, the search engines have gotten much better at choosing the canonical version and ignoring the duplicates. However, I've seen too many instances of search engines not always doing this properly, which means that you should make it explicit and not rely on the search engines to figure it out for themselves.

How to solve:

There is a URL rewrite module which can help solve this problem on IIS 7 servers. The tool has a nice option within the interface that allows you to enforce lowercase URLs. If you do this, a rule will be added to the web config file which will solve the problem.

Be careful not to overuse a keyword in your title or article body. You should not use a keyword more than 1 to 2 times per hundred words of content. There are some great tools online that will calculate your keyword density for you. You just copy and paste your article into one of these tools and it will automatically calculate the key words and their density in the article