Unit 407 Automated Constructor explains the puzzle:
Click the link for words in sequence in order to form a sentence. Namely, the following:
The first is a sentenced used to test fonts. It contains every letter of the alphabet at least once. The second is the ultimate question of life, the universe, and everything, according to the Hitchhiker's Guide to the Galaxy series. The third is an example, used in linguistics, of a sentence that is grammatically correct but completely non-sensical.