- Lose - Loose
- Their - They're - There
- Your - You're
- It's - Its
- Effect - Affect
- Weather - Whether
- A lot
- Then - Than
These are commonly misspelled words according to The Oatmeal. To know why, read his funny comic The Oatmeal - Ten Words You Need to Stop Misspelling.
Other comics relating to grammar and punctuation from The Oatmeal:
What it means when you say "literally"
When to use "i.e." in a sentence
How to Use an Apostrophe
Ten Words You Need to Stop Misspelling