i want to know wather they are any expoits and hacking techniques for gmail or orkut and if they are any then what are they and how to protect ourselfs from them.

Could you explain a little bit more what you mean by "expoits and hacking techniques" ...if you mean something like cracking password or demage other users account or then you should know that it is simply an illegal thing and more immoral thing thats why here no one is going to help you in that matter , and more ever you can get warning from mods of this forum etc.

Weird question. Even if there is an exploit discovered, it will be made known and patched extremely fast. Basically there isn't any much you can do to help yourself with those exploits. Just have a good firewall, anti-virus and anti-spyware programs installed should be enough to keep your computer healthy. The main part will be patched by Google itself, hence you will not need to worry.