How to troubleshoot web errors on the Apple developer forum?
Usually things like that are caused by browser extensions or an odd interaction between a specific browser version and the code on the site.

Have you looked over the basic support page for the Developer Forums?

https://developer.apple.com/support/resources/developer-forums.html

It has a "contact us" form if you can't solve this by ensuring an up to date (and unmodified) version of Safari isn't rendering the web site properly for you.