Uppercase URL's the pitfalls
It is good practice to avoid including capital letters in your URL structure and there is good reason for this. Take the following URL http://www.example.com/Home/Article. The problem does not lie with the domain part as this is not case sensitive. The path part is where the issue lies depending on server environment. Generally Windows servers are not case sensitive and can process the URL without any problems i.e it will deal with http://www.example.com/home/article in the same way as http://www.example.com/Home/Article. Although the URL's are different, as long as they are spelt the same they will both take you to the same content. The problem arises with the search engines as they can view this as duplicate content and this is something that should be avoided.
If a website is developed on a Windows server and a mixture of uppercase and lowercase URL's are used to point to the same resource, problems can arise later if the website is moved to a UNIX based server. As UNIX is case sensitive unlike Windows http://www.example.com/home/article and http://www.example.com/Home/Article would be seen as two different resources, this will result in a broken link to one of the URL's.
Uppercase URL's Resolution
If a website has a mixture of both uppercase and lowercase URL's the best way to resolve this issue is to use a 301 redirect to redirect all URL's with uppercase characters to a lowercase alternative. This will ensure that any link weight is passed to the lowercase URL, it will also ensure visitors will be redirected to the correct page even if they type in a capitalized URL.
Uppercase URL's Best practice
The best way to avoid any issues regarding capitalization is to engage in the practice of only using lowercase URL's on a website. It will prevent any problems and is also the favoured SEO friendly method.