Are you using commas in your URLs? Here's what you need to know.

• I just took on a "mom and pop" client who did all its own site design and URL structuring. They have URL structures all over the place and even have URLs with commas in them (which I'd never seen). They don't seem to be a problem, but I'm sure this isn't good. Am I right?

Answer: While it's definitely possible to use commas in URLs, it's not a widely used practice, nor is it recommended.

First, from a user standpoint, most will have trouble understanding the placement of a comma within the common URL structure because, unlike hyphens or underscores, they are not an ordinary URL parameter. Notice the difference visually when confronted with the two URLs below (one with commas, and one without):

http://www.yoursite.com/category/keyword1,keyword2

http://www.yoursites.com/category-keyword1-keyword2

When it comes to most online users, anything out of the ordinary can make them wary of a Web site. And with our example above, just seeing a comma-delineated URL may cause site visitors to click away.

And why wouldn't they? Users aren't familiar with commas in URLs because they aren't normally used as part of the hierarchy in a link. They can, however, be used to delineate subcomponents within a URL structure.

Commas are considered to be "reserved" characters for HTML, which include dollar signs, ampersands, pluses, semicolons, etc. These reserved characters can be used in creating URLs but they need to be encoded. Here's a quick chart listing these reserved characters and the comma's place among them:

Typically, these "reserved" characters will be used in dynamic URLs that are part of a large ecommerce or product based Web site. For example:

http://www.sample.com/forum/read.php?13,35869

As you can see, the comma is used after the query to organize the URL but there may be better ways to organize t...