Identify a "good" website by these characteristics 

AUTHORITY and ACCURACY
•    Who publishes the website?  Is this a well-know or respected institution?
•    Is there contact information for authors of the website content?  What is their background or credentials?
•    Is it a commercial site (.com), a government site (.gov), an educational site (.edu), a non-profit or other organization (.org)? How does this affect  the information presented?
•    Do other reliable sites link to this one?
•    Are facts, ideas or references credible and backed up by citations to the original sources?

PURPOSE and OBJECTIVITY
•    What is the purpose of this site: to sell, inform, entertain or persuade?
•    Who sponsors this website?  What is their agenda or goal?
•    For what audience is this site written?
•    Is there an explicit or hidden bias behind the information presented?
•    Is there advertising on the site? Does this influence information found on the site?
•    Are arguments well-reasoned and supported?

CURRENCY
•    Is the information on the page up-to-date?
•    Is the page updated regularly?
•    Are there dead links?

Examples of websites, at least partially dedicated to biomechanics:

There are many authoritative government and non-profit health and medicine websites around.  Here are a few: