When cameras follow you pretty much 24/7, why on earth would you lie about what you're doing? Kirsten Dunst got caught in a web of lies this week when she fibbed about why she bailed on Monday night's Spider-Man 3 screening. "She told everyone she was sick and left right after the red carpet," a spy tells Page Six, "but really she went to her birthday party." Yes, it's unfortunate that her birthday fell on the night of the premiere, but she parties, like, every night -- couldn't she take one night off, or at least go out after the screening? Man, that girl has a Spotless mind