By far the most common is a browser showing you a saved copy of your own page. Browsers do this deliberately to make the web faster, and it means the person most likely to see an out-of-date version of your site is you, because you visit it more than anybody.
The second most common is looking at the wrong thing: the editor rather than the live site, or an old tab, or the shared address rather than your own domain. Both are worth ruling out before assuming something is wrong.
What to tell us. The address you opened, what you expected, what you saw instead, and roughly when. A screenshot settles it faster than anything else. Email hello@kitsetlabs.nz.
Step by step
Reload properly. Hold Shift and press reload, or open the page in a private window.
Check you are looking at the live site, at the right address.
If you just published, give it a minute.
Try it on your phone on mobile data. If it works there, it is your browser or your network rather than your site.
If it does not go to plan
My site is completely down.
Tell us straight away. We watch for that and alert ourselves, but if you notice first we want to know.
It is broken only on one person's computer.
Almost always their browser holding an old copy, or a work network blocking something. Ask them to try on their phone.