How to use titles instead of IDs in urls for nodes? I am managing a site right now (Drupal 6) and the links are all coming out in the form http://example.com/blog/12553.

I'd like these urls to be based on the name of the article. I could swear that the site used to do this, but not sure at all where to find this setting or what might have gone wrong. I was looking into 'clean urls' but conclude that the urls are clean (Because they don't have PHP parameters), but I'm not sure.

I'm pretty familiar with PHP and programming... less familiar with Drupal
You should check to see if the pathauto module is installed. If not, I highly recommend downloading, installing and enabling it... It should make very short work of this.

Here's the link for d6

https://www.drupal.org/node/17345/release?api_version%5B%5D=87

If it is already enabled... then you may have more trouble as the d6 version is no longer maintained... so you may need to do some troubleshooting of this module.