<!DOCTYPE html> <html reftest-async-scroll reftest-displayport-x="0" reftest-displayport-y="0" reftest-displayport-w="800" reftest-displayport-h="2000" reftest-async-scroll-x="0" reftest-async-scroll-y="100"> <style> html { overflow: hidden; } #section { padding-top: 1px; } #header { position: sticky; top: 0; } #header > div { margin-top: -50px; border: solid blue 2px; height: 100px; width: 100px; } #spacer { height: 1500px; } </style> <div id="section"> <div id="header"> <div></div> </div> <div id="spacer"></div> </div> </html>