The document summarizes 10 common grammatical errors:
1) Subject-verb agreement errors where the subject and verb do not match in number.
2) Sentence fragment errors where a sentence is incomplete and missing an independent clause.
3) Comma errors where commas are omitted after introductory words or clauses.
4) Apostrophe errors in contractions like "it's".
5) Comma errors in compound sentences where commas are omitted before conjunctions.
6) Misplaced or dangling modifier errors where a modifier is separated from the word it modifies.
7) Vague pronoun reference errors where the antecedent a pronoun refers to is unclear.