When proofreading written content, it's essential to watch out for various grammatical and punctuation errors to ensure accuracy and clarity. Here are four types of common errors to look for:

Subject-Verb Agreement: Check that the subject and verb in a sentence agree in number (singular or plural). Incorrect subject-verb agreement can lead to confusion and grammatical inaccuracies.
Punctuation Errors: Look for mistakes in punctuation, including missing or misplaced commas, semicolons, periods, question marks, exclamation marks, and quotation marks. Correct punctuation is crucial for conveying meaning and maintaining proper sentence structure.

Run-on Sentences and Sentence Fragments: Check for run-on sentences (sentences without appropriate punctuation between independent clauses) and sentence fragments (incomplete sentences that lack a subject, verb, or complete thought).
Spelling Mistakes: Carefully review the text for spelling errors, as misspelled words can negatively impact the readability and credibility of the content.