Better yet, if I start at the Google results page for "php array filter" and click the top link, it takes me to:
http://php.net/manual/en/function.array-filter.php

Then, when I click on "array filter" on the side menu, it takes me to:
http://www.php.net/manual/en/function.array-filter.php

and if I click that same link again, it takes me to:
http://us3.php.net/manual/en/function.array-filter.php
and now the CSS has changed.

Please clarify what you mean with different CSS. Maybe screenshots
would be helpful (you'd have to upload them elsewhere, and add links
in this ticket). And please note which browser you're using.

Anyhow, on a slow internet connection I experience different fonts
until the page is completely loaded. That is, however, to be
expected because downloadable fonts are used with fallbacks to
built-in fonts. Maybe in your case the fonts fail to be loaded?

The only difference I saw between the 3 links (php.net/www.php.net/us3.php.net) was that in IE9 it had the right scroll bar visible always and it was on us3 only, but that was merely something, and probably a browser thing

It is the way the mirrors are selected that affects how www. is translated. Currently all MY www.pages map to uk1. so different people will see mirrors. Accessing the mirrors direct will give different results depending on how your browser is set, or is that the www. one? Changes to the CSS are incidental, it's the mapping of the mirror which is perhaps going wrong, but we did establish that browser settings mess things up.

Lester, can you please, and I mean PLEASE don't change topics in bug reports and instead report a separate issue or mail php-webmaster? Thanks

Kalle - why is this changing the subject. The problem is that the browser is seeing different cached copies of the CSS depending on where it is redirected. It's something we have seen before and your seeing something different is because of it.

OP here. I tried again today and I'm not seeing the bug...
Google now takes me to
http://php.net/manual/en/function.array-filter.php
and clicking on the nav link to "array filter" takes me to the same page.

Browser: Google Chrome Version 45.0.2454.85 m
OS: Windows XP

Maybe it was a slow connection problem like that other guy said?

p.s. the CSS change appeared to be only a font change. Should have been more specific.

I guess it could have been a slow connection and our font wasn't loaded in, please re-open if it continues, thanks! :)