Grammar police: top 5 grammar mistakes

By Hannah Moss

Top 5 grammar mistakes

What happens when you make mistakes in your web copy? Ultimately, you could lose customers. Here are the 5 most common grammar mistakes and how to avoid them.

Many of our previous posts have focused on the importance of publishing good quality, regular content on your website, such as 7 steps to writing a great blog post and How to write killer headlines for your blog.

You know how important it is to write interesting, relevant content to engage your audience and keep them coming back for more. But did you know how important it is to have good attention to detail in your writing?

Good grammar is becoming a lost art

In these days of rapidly advancing technology, spell checks and text speak, it seems that good grammar is becoming a lost art. But publishing a blog full of typos and poor grammar sends a very bad message to your readers. If you can’t get your English right, how good will the service be that you provide? If your attention to detail is poor on your website, what kind of attention can a customer expect to receive from you?

You may think that having a good command of English isn’t so important these days, as people tend to scan read text, skim over content and be more influenced by images, video and other types of content. But this couldn’t be further from the truth.

The subtleties make all the difference

I actually believe that, as our lives get busier and our time gets more precious, it’s even more important to get the details right. And this includes the right language with the correct spelling, grammar and punctuation. People want to make decisions quickly. There’s so much competition that they need a product or service to stand out. They need to go with their gut and choose a provider that feels right for them. So it’s the subtleties that make all the difference.

How many times have you visited the website of a company that’s offering something you want, only to dismiss it because it doesn’t look very nice, or it’s too confusing, or you don’t like the way they come across? You may even have disregarded them because of the language they use. And I can almost guarantee that at some point this has included errors you’ve spotted, even subconsciously. An error in language can be just as damaging as a broken link, or a page that won’t load.

If your grammar is correct and you’ve used the right tone of voice, the chances are that your readers which will be much more inclined to revisit your site, develop a preference for your business, and eventually become regular customers.

5 common grammar mistakes

I could write a whole book on common grammatical mistakes! But let’s put the world to rights one step at a time by focussing on the top 5.

1. Apostrophes

Apostrophes are by far the least understood and most misused grammatical element of all time. Oh, how I abhor a misplaced apostrophe! Once you ‘get’ them it’s pretty simple really, but I know how confusing they can be. So here’s the lowdown.

There are only 2 reasons an apostrophe is ever used:

  1. Ellipsis – to indicate a missing character from a word.
  2. Possession – to indicate something belongs to something else.


We use an apostrophe to indicate ellipsis when we want to contract 2 words together, e.g.:

  • can not > can’t
  • I am > I’m
  • it is > it’s*
  • will not > won’t
  • we are > we’re
  • let us > let’s
  • should not > shouldn’t

* The reason it’s and its get so confused is because these are examples of ellipsis and possession respectively, but it’s the one without the apostrophe that indicates possession, e.g.:

  • It’s not right that people should make so many mistakes. (Ellipsis: it is)
  • The dog wagged its tail. (Possession: the tail of the dog)


We use an apostrophe to indicate possession when one object or concept belongs to another, e.g.:

  • the cat’s tail > the tail of the cat
  • Daisy’s book > the book belonging to Daisy
  • my ship’s anchor > the anchor of my ship
  • the politician’s policies > the policies of the politician
  • his boy’s ideas > the ideas of his boy
  • the school’s principles > the principles of the school
  • the earth’s rotation > the rotation of the earth


I cannot mention apostrophes without mentioning plurals! The rule of thumb here is:

Apostrophes are never used to indicate plurals


  • Incorrect: We enjoyed the potato’s.
  • Incorrect: The new t-shirt’s arrived.
  • Incorrect: Mr Jones liked his new boot’s.

The only time apostrophes are used with plurals is to indicate possession, in which case the apostrophe goes after the ‘s’.


  • Correct: We enjoyed the potatoes’ firm texture and smooth taste.
  • Correct: The new t-shirts’ fabric was very good quality.
  • Correct: Mr Jones’ boots were to die for.

N.B. Dates and acronyms should never have apostrophes (unless in a context of possession), e.g.:

  • 1980s (not 1980’s)
  • 2000s (not 2000’s)
  • DVDs (not DVD’s)
  • B&Bs (not B&B’s)
  • WCs (not WC’s)
  • BBQs (not BBQ’s)

2. There/Their/They’re

These homonyms seem to stump people all too often. The rule here is:

There = place

Their = possession

They’re = contraction


There is an adverb indicating a place or position, e.g.:

  • There are no trees where we live.
  • We went to Spain and lived there for a year.


Their is a determiner belonging to or associated with the people or things previously mentioned, e.g.:

  • The children thought their parents very elderly.
  • The chickens laid their eggs every morning.


They’re is a contraction of they are. As mentioned above, the apostrophe here indicates ellipsis, e.g.:

  • They’re determined to get it right this time.
  • My twins are nearly 6 – they’re growing up so quickly!

3. Comma splice

The comma splice is by far the most common misuse of the poor little comma! It occurs when 2 independent clauses (both with a subject and verb) are joined incorrectly with a comma, e.g.:

  • Incorrect: The plant was dying, it needed water and sunlight.

Both these clauses could stand alone as a sentence, so they cannot be joined with a comma. Instead, a full stop, semi-colon or dash should be used, e.g.:

  • Correct: The plant was dying. It needed water and sunlight.
  • Correct: The plant was dying; it needed water and sunlight.
  • Correct: The plant was dying – it needed water and sunlight.

The only time you would use a comma here, is if you added a coordinating or subordinating conjunction, such as: and, but, or, yet, so, as, because, if, since, etc., e.g.:

  • Correct: The plant was dying, as it needed water and sunlight.
  • Correct: The plant was dying, since it needed water and sunlight.
  • Correct: Because it needed water and sunlight, the plant was dying.

4. Affect vs effect

It’s amazing how often these 2 get mixed up! Put simply, affect is a verb meaning to do something that causes an effect, which is a noun, e.g.:

  • Correct: My hearing really affects my balance.
  • Correct: My hearing has such an effect on my balance.
  • Correct: The news of her neighbour strongly affected her.
  • Correct: The news of her neighbour had a strong effect on her.

Tip: the ‘a’ in affect also stands for action, which is what verbs do.

5. Should/could/would have

This phrase is misused so often, I dread that one day it will find its way into the dictionary. Let’s stop that from happening!

In a nutshell, the phrases should of, could of and would of do not exist in the English language. The correct use of the phrase is should have, could have and would have. The reason this is often misused is due to the sound of the contraction when spoken: should’ve, could’ve, would’ve, e.g.:

  • Incorrect: I should of known.
  • Incorrect: You could of told me.
  • Incorrect: We would of loved it there.
  • Correct: I should have known. (I should’ve known.)
  • Correct: You could have told me. (You could’ve told me.)
  • Correct: We would have loved it there. (We would’ve loved it there.)

Got a grammar question?

I hope you’ve found this post useful and it’s cleared up some grammatical confusion for you.

If you have a grammar question or there’s a use of English you don’t quite understand, contact us and we’ll feature the answers in our next Grammar Police post.

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