Hello, I am newbie in web designing
I would like to know about some IMP TOS that are generally used while giving quotation of website designing service.

One of the main TOS rules are

"Please do not remove our copyright from your final website design, unless you have purchased copyright removal from us"

or words to that effect.

TOS can be used for a variety of uses from a legal standpoint. Also you can reference them in your contacts so you're not duplicating your TOS in every contract. Also you can update them if you've specified that in your documentation to allow for things you didn't realize until later. Just make sure that you keep your customers/clients appraised of changes.