Thanks for the help Willr. I did as instructed, which provided a detailed Error message listing a problem with a php file in sapphire/core/ directory, which didn't make sense because I only touched tutorials/template/ files and the mysite/code/ files.
But as the mysite/code/ directory also contains php files, I figured I had a misnamed file in there. So I opened up one of the files I created in there in tutorial 2, commented out a php line, saved the file, refreshed the browser to find a much longer and more detailed error message. so I undid my commenting out, saved the file, refreshed the browser to find the original error message gone. I don't know what fixed it.
And continued on with tutorial 2, or tried to, until my lack of knowledge of php got too difficult and I decided I really need to understand php more before continuing... I hope to come back soon.