Errors & Troubleshooting

A blank page with one line of text, and five possible causes. Here is how to tell which one you have, in the order worth checking.

Support will often ask for this first, because a stale cached copy of a page is a surprisingly common cause of a fault that has already been fixed.

Nothing on the page at all, not even an error — here is how to make the failure describe itself instead of hiding.

Time to first byte measures how long the server thinks before it answers at all, before a single image or line of CSS is even requested.

PHP hit its memory ceiling and stopped rather than risk taking the whole server down with it — here is what to do about it.

PHP tried to send a header after the page had already started printing content — here is how to find exactly where that content began.

A script ran for longer than PHP allows and was stopped mid-task — here is how to give it more time, or find out why it needed it.

The server is doing exactly what it should — refusing a file it has not been given the right access to. Here is how to grant it correctly.

Somewhere between one page and the next, the server stopped recognising you as logged in — here is why that happens and how to stop it.

One heading covers several completely different faults — here is how the small print underneath tells you which one you actually have.

Nothing answered on the other end at all — here is how to tell whether that is the server, the address, or something on your own network.

Your browser could not turn the domain name into an address at all — here is how to work out why DNS has nothing to give it.

Your browser gave up after looping between the same handful of URLs — here is how to find which one is sending you back.

A page full of broken image icons could be a wrong path, a permission, or a blocked request — here is how to tell them apart.

A stuck progress bar or a rejected file could be five different things — here is how to work out which one you actually have.

The server saw your request and refused it on purpose — here is how to find out which rule is doing the refusing.

The server looked and found nothing there — here is how to work out whether the page moved, was deleted, or was never really at that address.

The least informative error on the web. The real message is always in a log — here is how to find it and what it usually says.

One server passed your request to another and got back garbage — here is how to work out which of the two is actually at fault.

The server is telling you it is temporarily unable to cope — here is how to tell a stuck maintenance flag from genuine overload.

Something upstream took too long to answer and the gateway gave up waiting — here is how to find exactly what was slow.

Apache reads this file on every single request, so one invalid line breaks the whole site the moment it is saved.

The browser blocked the request on purpose, as designed — here is how to tell which side actually needs to grant permission.

The domain resolved fine — something between you and the server simply never answered in time. Here is how to find where.