Core (rhymes with "poor" English) Performance.com

The tag on a new Adidas sleeveless workout jersey invited the purchaser to a free three-week trial at coreperformance.com. The Adidas affiliation implies a measure of quality and professionalism. 

But the site featured subliterate copy gaffes like "dos and dont's." That one was bound to happen sooner or later, what with all the crazy, ignorant use of apostrophes to make words plural. The apostrophe denotes the possessive, as in belongs to, or a contraction as in don't do not. The apostrophe is not used to pluralize words except by those for whom English seems to be their second language, even when it is is not.   

Ironically, whomever wrote the above did not commit the commonplace "do's" but managed to misplace the apostrophe in  "don't."

In another place of the site, the word assessment is misspelled as "assesment", so at least the person who is butchering the English language at Core Performance is consistent -- consistently not up to the task they are paid to do. Double-duh on the culprit.