By default, the URLs that are generated by WordPress are not that great. When you first install WordPress, the main types of URLs will look as follows:Posts: www.yourdomain.com/?p=1Pages: www.yourdomain.com/?page_id=2Categories: www.yourdomain.com/?cat=1While these URLs may not look that bad to you, there are a couple of reasons why these URLs are far from being optimal. To begin with, they do not provide much information to users. Not only can this cause confusion when a user mouses over one of these links, but it can also make them less likely to link to a post or page on your blog (or at the very least, it will be more difficult for them).The other problem with these URLs is that they are not search engine friendly. Having properly optimized URLs can help you rank higher in Google and other search engines for specific terms related to your blog, but having URLs in this default form is not going to provide you with any benefits.Although it provides you with ugly default URLs, WordPress does do a good job of making it easy to change these URLs to a more friendly form. In order to do this (these instructions will be based off of WordPress 2.7, but the process should be nearly identical for older versions of WordPress), you will first need to log into your WordPress Dashboard. Next, click Settings (which can be found on the left side of the page), and then choose Permalinks from the drop-down menu that appears.As you will see, WordPress provides you with an easy to use interface that allows you to change your Permalink structure. In addition to the Default option, WordPress provides you with three other options. Although Day and name, Month and name, and Numeric are the first three options provided, I actually recommend using the fourth option, which is Custom Structure.If you visit the WordPress Codex, you can find all of the tags that can be used for the Custom Structure option. While I recommend taking a look at the Codex, here are the two Custom Structure options I recommend:The structure I personally use is /%postname% , which creates URLs that look like www.yourdomain.com/my-first-blog-post.Although I don’t personally use this structure, another popular option is /%category%/postname, which creates URLs that look like www.yourdomain.com/ramblings/my-first-blog-post.While it’s best to make these changes before you start publishing any content on your WordPress blog, even if you have a blog in existence, it’s not too late to convert your URLs. Since you want to avoid breaking any of your existing URLs (which could cause a headache for users and make search engines unable to index your content), you will want to use a plugin that not only updates your URL structure, but properly redirects URLs for users and search engines. The best plugin to achieve this task is the Permalinks Migration Plugin, which allows you to pick a new URL structure and then uses a 301 redirect to properly handle all of the old URLs.