Common Mistakes : Downstairs

adverb

.BAD: I ran to downstairs and picked up the telephone
.GOOD: I ran downstairs and picked up the telephone

.BAD: The dining room and kitchen are in the downstairs
.GOOD: The dining room and kitchen are downstairs

: Downstairs and upstairs are usually adverbs and are not used with to/in/at etc
.The bathroom is upstairs
.I ran upstairs to see what all the noise was about