Supporting Documents: Certified or Notarized??

I am wondering if someone can tell me if I need supporting documents to be certified or notarized (offers of accommodation, property deeds, etc.). I talked to solicitors in the UK and they indicate that having a document certified is a very easy and inexpensive process (while you wait). Getting a document notarized seems a little more pricey and not every solicitor can do it. Can someone with experience tell me what I need?

I recently got my spouse visa. The only thing we had to get notarized was my husband's passport copy and that's because it was a copy. At first we just had a third person write that it was a true copy, date and sign it and that was insufficient. The Ottawa office emailed and said they required either a properly notarized copy or the original.
The other documents we sent were originals and did not need to be notarized.

hey ! , how long after you gave your notarized copies of the passport did you get your visa?
I got an email asking me to send my husbands notarized copy today, but i paid for priority services and really need my passport within the next 2.5 weeks. i was wondering if it will take them long once they receive the documents ?

It took exactly 2.5 weeks to receive my passport, BUT I just sent the notarized copy back to Ottawa by regular post so hopefully you will get yours sooner.