S.H.
My daughter started learning when she was about 3 or 4 (she's 5 now). She is a pro with Nick Jr.'s site and PBS Kids site. I would get her started on what she wanted & she would go from there. Then I bookmarked the 2 pages and taught her how to go to click on them. I had put them in a folder with her name in all caps so she would recognize it!
Then I ended up teaching her how to open Firefox by herself. They catch on quick!