Few days ago i watched a youtube video about how to do squats properly. I followed those steps and did squats but later on i felt pain just above my knees. I was not even able to stand up properly for sometime. Is such kind of pain normal when doing squats or something was wrong?
I've had similar knee pain in the past (post-workout strain above the knee, achey pains at the side, and sometimes a warm hot feeling under the patella) until I learned to adjust squat techniques for my body.
So, in case Mohit is a woman (sorry, Mohit, I don't know if yours is a female or male name), or in case a woman is reading wanting to avoid the kind of knee pain Mohit speaks of, just let me add into the mix a women-specific training tip for squats that has helped me get past pains like that:
From 'Free Standing Barbell Squats' in Anatomy for Strength & Fitness Training for Women by Mark Vella
... women are more prone to knee injury than men. This may be due to the wider pelvis of women and the more angled femur to the knee joint that renders women's knee joints less stable during exercise movements. Adapting the squat to suit a woman's body is therefore important to obtain safe and effective results.... place your feet wider than shoulder-width apart in the starting position.
And while that is a woman-specific response, all male bodies are individual as well. If following otherwise good form is still not working and those kinds of knee pains persist, a man could also benefit from experimenting with a wider stance, as his individual pelvis width/angles/ratios/etc., might require him to make adjustments and do what is right for his body.
It seems to me that the trainer in the video you posted does not stress the importance of coming down to parallel with your knees. He only seems to use this point as a limit for how deep you should squat. Now with that being said there is a possibility that you made no effort to actually reach parallel on every rep which I think can be cause for the knee pain, and here is why.
In his video on how to squat, Mehdi describes in detail the importance of coming down do a deep squat where the crease in your hip is actually lower than your knees. He says that a major cause for knee pain when squatting is from the muscular imbalance that can occur when one does not squat deep enough. Meaning, if a person does not come down to parallel then the only muscle that gets worked is the quad, but that hamstrings which work opposite the quads don't get stimulated at all, and this causes a muscular imbalance which then can lead to injury. However, if you do come down low enough, then you will feel a nice strong stretch in the hamstrings and that should help get rid of the knee pain. http://www.youtube.com/watch?v=VnV7vEi7Sz8 This is the video I mentioned where Mehdi explains how to squat properly. It's a little bit long, but very clear and concise, and should totally clarify the squating concept for you.