Here are 10 of the most common mistakes in English with explanations and examples.
It's vs. Its
Two, Too, To
They're, Their, There
You're vs. Your
Confusing Words
Since vs. For
Have vs. Of in Conditionals
Has gone to vs. Has been to
Then vs. Than
Double Negatives
See also 5 Top Common Writing Mistakes of English Learners
Resources from: http://esl.about.com
It's vs. Its
Two, Too, To
They're, Their, There
You're vs. Your
Confusing Words
Since vs. For
Have vs. Of in Conditionals
Has gone to vs. Has been to
Then vs. Than
Double Negatives
Resources from: http://esl.about.com