Declaring your page language: the lang="en-AU" attribute
At the very top of your page's code, the <html> tag can carry a language declaration: <html lang="en-AU">. Plenty of older small-business sites have none.
Why it costs you customers
Screen readers use it to pick the right pronunciation voice — without it, assistive software guesses.
Browsers use it to decide when to offer translation; search engines use it as a weak locale hint. None of these is dramatic, but the fix costs one minute.
Check it in 30 seconds
View source; the first line or two should read <html lang="en-AU"> (or at least lang="en").
Our free check reads it automatically.
How to fix it
Edit the opening tag: <html lang="en-AU">. Done.
Wix/Squarespace/WordPress set a site language in general settings — make sure it is actually set to English (Australia) rather than the default en-US, then the attribute follows.
This is a good "while the bonnet is open" fix: nobody should pay someone to do only this, but any time you or a developer touch the site header for other reasons, spend the extra minute.