Nobody emails you to point out a stray comma. But readers notice, even if they can’t name the rule you broke, and a page full of small punctuation mistakes reads as careless – which makes people trust the content less, even when the actual information is solid.
The apostrophe mix-up that shows up everywhere
“Its” versus “it’s” trips up more writers than any other punctuation mistake. “It’s” is only ever a contraction of “it is” or “it has.” Everything else – possession, ownership, “the dog wagged its tail” – takes no apostrophe. The fastest check: read the sentence and mentally expand “it’s” to “it is.” If that sounds wrong, drop the apostrophe.
Comma splices: two sentences pretending to be one
A comma splice happens when two complete sentences get joined with just a comma instead of a period, semicolon, or connecting word. “The article was long, it still ranked well” should be “The article was long, but it still ranked well” or split into two sentences entirely. This is one of the most common punctuation mistakes in first drafts, because it mirrors how people actually speak.
The Oxford comma debate (and why it’s not just a style choice)
Whether you use a comma before the final “and” in a list is genuinely a style choice – until it isn’t. “I’d like to thank my parents, God and my sister” reads differently from “I’d like to thank my parents, God, and my sister.” Pick one style and use it consistently across your site so readers aren’t distracted by inconsistency from paragraph to paragraph.
Semicolons used where a period would work better
Semicolons connect two closely related complete sentences. They are not a fancier comma, and using one to join a sentence with a fragment is a common misstep. If you’re not confident about a semicolon, a period usually does the job just as well and reads more naturally online.
More Mistakes Worth Knowing
Missing comma after an introduction
When a sentence opens with a phrase such as “After the update” or “In most cases”, a comma usually follows it: “After the update, traffic increased.” Without it, long sentences become harder to read.
Apostrophes in plurals
Plural words do not take an apostrophe. Write “three tools”, not “three tool’s”, and “the 1990s”, not “the 1990’s”. An apostrophe shows either a missing letter (“don’t”) or ownership (“the writer’s draft”).
Mixing up your and you’re, their and they’re
These are spelled correctly, so spell check ignores them. Expand the contraction to test it: if “you are” or “they are” fits, use the apostrophe form.
Hyphens and dashes
Use a hyphen to join words into one idea (“well-known author”, “step-by-step guide”) and a longer dash to add an aside. Do not hyphenate an adverb ending in -ly: write “a highly useful tool”, not “a highly-useful tool”.
Quotation marks and other punctuation
In American English, periods and commas go inside the closing quotation mark. In British English, they usually go outside unless they belong to the quote. Choose one convention for your site and keep it.
Too many exclamation marks
One can add energy. Several in a row look like shouting and weaken the message. In professional content, use them rarely.
A Quick Punctuation Self-Test
- Read the sentence out loud. A natural pause usually means a comma, and a full stop in your voice means a period.
- Look for two complete sentences joined only by a comma.
- Search for every apostrophe and ask whether it shows a missing letter or ownership.
- Check that lists use the same punctuation style throughout.
Sentence structure matters as much as punctuation, and our guide to sentence length and readability shows how to keep it clear. Before you publish, follow the routine in why proofreading before publishing matters.
Catching these before you publish
Proofreading your own work is hard precisely because you already know what you meant to say, so your eyes skip past the mistake. Running the final draft through a punctuation checker catches the apostrophes, comma splices, and stray semicolons a tired read-through misses, before the piece goes live rather than after a reader points it out.