I see a lot of mistakes in online articles, even well known newspapers, and books. My theory is that there are no human proof-readers left, and it is all done by software. So if the article has "their" instead of "there", the software recognizes it as a word and can't figure out it is in the wrong context.
My pet peeve about recipes is when you get one that looks like this
milk eggs
butter sugar
with appropriate amounts, and then as you are reading the block of text under the ingredient list, there are more ingredients hidden in there. No, put all the ingredients up front so I can scan them and see if I have all of them.