Using this is a good idea, although it might be more apropos to use the original page and have the help be custom to the button/links. The links from the words Action, etc., all point to the help. The idea was to be more verbose. The original help is here:
So, after some more thought, I agree that the best way to fix this is to get the www.opendap.org/online_help_files/opendap_form_help.html link to dereference to https://opendap.github.io/documentation/QuickStart.html#_an_easy_way_using_the_browser_based_opendap_server_dataset_access_form.
I looked at how that might work, but can't figure it out right away; Nathan asked Keith, I did too.