Thank you everyone for replying. I am currently using the ® on every usage but I might change that since two of you pointed out it is only needed once.
The biggest reason I asked is that I want to enter this year's site in the website award category and proper usage earns you more points.
I also wanted to check because on the website feedback I received last year one of the evaluators mentioned that there was no copyright statement and that I needed one. I'm still confused about that comment but I want to try and get it right this year.
Thank you again.
