i ride my bike 20 minutes a day, when i am riding an a rough pavement, ill get like one skip or slip, but not all the time. very rarely it happened. is it considered to be normal for a bike.
If it's a single speed is the chain tension correct? A loose chain can skip in the conditions you describe.
If it is a multi-geared bike and skips get the chain stretch checked out at a bike shop. You may need a new chain. They can check and install the new one for you.
No not normal. Measure the distance between the links on the chain. At the 1 inch mark on your ruler the the two rivets should be dead on. If it's a little more than one inch then your chain is stretched and needs replacing. That will take care of the problem.