Documentation performance problems in Firefox
Some documentation pages, especially those with multiple images, are very slow when scrolling. This process is very CPU-consuming and allocates huge amounts of memory (hundreds of MBs per second up to several GBs; it could lead to killing the browser by oom_killer).
These problems occur only in Firefox (version 86.0 in Linux). They probably don't affect browsers based on Webkit/Blink (tested in Chromium, Opera and Rekonq).