"Your welcome." Aaiiiieeeee! Please kill me now.
This is an error that seems to be an epidemic at all levels of society, especially on e-mails.
- "You're" is a contraction of "you are."
- "Your" modifies nouns, and in "your house."
- "It's" is a contraction of "it is," as in, "It's a beautiful morning."
- "Its" is used to modify nouns, as in, "The cat uses its litter box."
These and other common confusions are listed in Harbrace's Glossary of Usage, (G-1 through G-11, near the back, marked usgl on the upper right corner of the right-hand pages.