Does it make any difference to SEO ratings what-so-ever if your url has a trailing slash:
as opposed to one that does not:
Read the full blog post by Google here, http://googlewebmastercentral.blogspot.com/2010/04/to-slash-or-not-to-slash.html, it covers this exact topic.
Long story short Google does not care if you have a trailing slash. However, it will treat the below 2 paths as separate pages.
If you need to have both of the above and they are the same content your best option is to do a 301 Redirect to one of them from the other.
If that isn't an option you will want to add a
<link rel="canonical" href="your link"/> to both pages which will define which one is the master or parent. Matt Cutts has a great article here, http://www.mattcutts.com/blog/canonical-link-tag/, that covers the topic in its entirety.
In addition to RandomBen's point about search engines treating URLs with a trailing slash versus without as two different URLs, I'd like to add this. I generally use the trailing slash to indicate a category, while I don't use a trailing slash for pages that are at the end or bottom of a hierarchy. Slash your categories, don't slash anything else. If you're rewriting URLs, this most closely matches the natural file structure. However, you should make sure that each category in your path exists, or you could end up with some confused and frustrated users. In your example URL, "some" and "slug" should both be accessible pages.
There is one case in which a trailing slash will help with search engine optimization (SEO). That is the case that your document has what appears to be a file extension that is not
.html. This becomes an issue with sites that are rating websites. They might choose between these two urls:
In such a case, I would choose the one with the trailing slash. That is because the
.com extension is an extension for Windows executable command files. Search engines and virus checkers often dislike URLs that appear that they may contain malware distributed through such mechanisms. The trailing slash seems to mitigate any concerns, allowing the page to rank in search engines and get by virus checkers.
If your URLs have no
. in the file portion, then I would recommend omitting the trailing slash for simplicity.
(This is the same answer I posted on StackOverflow)
URL's with and without slashes are treated as two different URL's. Its absolutely essential that you fix this to avoid duplicate content problems. Generally, this affects the whole site, as every page has a duplicate.
See rankings improve.