Commercial interests have much more difficulty delivering useful resources. The certainty with which we can make these judgements will astound you. They simply don't have the motivation. Only an individual would publish this, most likely not on the web but though a mailing list. We can make further snap judgements about web information from the way you get there.
Promotion is very difficult on the web.
It is hard to find information which is poorly promoted. The tools you use to reach information pre-determines the type and quality of information your will find. Search engines index webpages indiscriminately. Advertised websites must have a pay-off. Link pages also link to established websites but put more thought into the selection of resources.