You should always include the URL of the page with the error. Don't ever assume that the owner or Web developer will know what page you're looking at. If the URL is really long, or you've forgotten it, write down what you searched for or how you got to the page in question so that the owner can get to it easily.
If you don't include a URL, don't expect your request to be taken seriously. Most Web developers are working all the time, and don't have time to go searching for a page where they wrote "teh" instead of "the". Yes, it would be nice if it were fixed, but fixing that typo won't pay next month's rent, and completing the design due tomorrow will. If you include a URL, they can go straight to the page, fix it, and be done in a few minutes of downtime while they work on their current project.
Posted in: Web Design and Applications