Stupid mistakes Fanfic writers shouldn't make (though do)
Their: Their house was beautiful
They're (They are): They're beautiful
There: There is a beautiful house on the hill
Your: Your friends are idiots.
You're (You are): You're an idiot
To: We went to England.
Too: You went too far.
Were: Were you even listening?
Where: Where are you?
Rogue: We have a rogue agent.
Rouge (A colour): Her dress was rouge.
Loose: This knot is too lose.
Lose: If you lose this game, you pay the for drinks.
Its: Its head was large.
It's (It is): It's a great day for a picnic.
Weather: The weather is nice today.
Whether: Whether he wins or loses, it won't affect us.