Do you believe in love at first sight?

Have you ever been browsing the internet and came across a picture of someone who left a lasting impression on you that you started to think of them so much you'd also dream of them?! I read the person's profile too and they sounded so mature and nice but he hasn't been on since April 22nd, I'd love to feed my curiousity. What are the chances of him coming back ? I asked friends but they said NONE. I guess I'm hopeful.