Your slogan needs a lot of work. I've read through it half a dozen times, and can't figure out what you're trying to say. There are so many problems, I hardly know where to begin (sorry to be so blunt, but, I'm guessing you're soliciting candid feedback, so I may as well do my best to provide that).
Are you trying to say that you are a young company, passionate about what you do, and eager to serve its customers? If that's what you're saying, you've put the words together in the wrong order. Something like "Passionate young web developers at your service" would be much better.
That said, I still think it needs a lot of work. Here's why:
1) Young is a poor word choice. Sure, "young" can imply youthful and energetic, but it also conveys inexperience. I would be very hesitant to business with a company whose slogan emphasizes a lack of seasoned leadership.
2) "At your service" is something that a concierge might say at a hotel, or a waiter might say in a restaurant, but it doesn't seem to fit well with a web development company.
3) What do you mean by powers? It's very hard to determine what you are alluding to. The power of the web? The power of your developers? The power of your company?
4) Passionate may not be a good word selection, either. One online dictionary lists three meanings for this word. One is enthusiastic, which is fine, but the other two meanings are "easily aroused to anger," and "swayed by sexual desire". I don't think either of those are what you're trying to say!
I'll take a stab at offering an improved slogan: Dedicated to harnessing the power of the web for you.
Dedicated is a word I'd use instead of passionate; "for you" can convey "at your service" without sounding so trite. Harness implies that you are working toward letting your customers get all they can from the Internet.