If you're trying to upload an image to your website and it's too big, you'll get an error:
This is usually because the file size is too big or the dimensions are too large.
You can find the recommended size for your website images in the CMS.
From the dashboard, go to the Settings menu:
Go to 'Assets', then Image 'Transforms' on the next menu:
Here you'll see the recommended format and dimensions for each type of image used on your website.