Can a website contain a trademarked phrase? Why?

It can as long as it is not being used as a source identifier in a way that is confusingly similar to the trademarked name.

Yes, a web site can contain a registered trademark if either 1) the mark is owned or licensed to the owner of the web site or 2) the mark is used as part of a valid evaluation of or commentary about the goods or services and the owner of the web site acknowledges the ownership of the mark. The issue of whether a domain name that is identical to a registered trademark can be used by someone who doesn't have a right to the trademark is still up on the air legally. This is becoming a major problem and resolving it can be very expensive. Assuming that "TacoBakingRoom" is selling the same sort of goods or services that "Taco Baking" is, you can file a complaint with ICANN and/or whoever sold the domain name asking that the domain name be revoked. File one with the ISP who is hosting the site too. Send a cease and desist letter to the "TacoBakingRoom" as well. However, if the companies aren't in the same or similar businesses, each may be able to use its respective mark on-line.

To be safe - no. Trademark infringement (use without permission of the owner) is only actionable if it causes a likelihood of confusion to the public. The types of confusion are many - including a wrong impression that the trademark owner is affiliated with you or is sponsoring you and your website. Best suggestion to avoid federal court litigation - DO NOT USE A TRADEMARK THAT YOU DO NOT OWN.