Yours or Theirs

Grrrrrrrrrr.....we all make typos but lately I have seen just plain out misspellings that no spell check is going to pick up. It is the wrong usage of a correctly spelled set of words. Now I am NOT professing to be an English master, but people who are earning nice $$$ on blogs and websites or are attempting to sell their crafts, are blowing this and need a smack upside their heads!!! This is also not a case of the new lingo replacing the old. It is just using the words incorrectly.
The first group is your or you're. If you can substitute the words 'you are' in place of your and it sounds right then the spelling is YOU'RE.
For example:
1-Your house is nice.
2-You are house is nice.
#2 is wrong, so the spelling is YOUR, choice #1

1-Your due at the show by 5:00.
2-You are due at the show by 5:00.
#2 is correct so use YOU'RE...okay?!

Group 2...there, their, they're
They're there at their house....confused?
Again, if you can substitute 'they are' and it sounds correct, use THEY'RE. In my example: They are there at their house.
THERE...is a place/location word and inside is another location...here...tHERE. So if you are (or you're) referencing a place, use there.
Last one...their. They're there at THEIR house. Whose house? THEIRS!!! It belongs to them.

I just finished reading a popular craft blog with thousands of visitors monthly, thousands,  and both you're and their were misused. Don't rely on spell check. It will not pick this up but your readers may and be turned off by what you're
saying because you don't know how to right  write. And they also may not by buy!  English is fun.......... :)