Hi,
I noticed that some Hybrid bikes have front shock and some dont(like road bikes). what is the disadvantage to have front shock? does it make you go slower when riding on the pavement?
I started with comfort bike and been riding about a year or so now I want something with more aggressive position and something faster on the pavement. I'm not quite sure of disadvantage of the front shock...

The front shocks do nothing on pavement except for eat up your pedaling energy. My bike has one (until I get the money for a new rigid fork) and it's not super noticeable except on hills.

The suspension forks cost more and weigh more and represent another mechanical thing that can break/wear out.

But they provide a smoother ride on rough surfaces. Sometimes that's important, and sometimes it isn't. You have to decide what's important to you.

spot on. I got rid of mine and put a rigid on my trek 7300. Best upgrade ever. I improved my ride and reduce the weight of my bike by 4 lbs.

Takabrash, based on the bike, more than likely will have a 1" headset and will be a pain to find. My LBS found me a steel rigid fork that got pulled from a Trek FX that the new owner swapped for a carbon fork. They sold it to me for $25. Might inquire around if they have any that will fit yours bike. It cost me $140 total. Fork, headset, stem and labor.