Sticky table headers: the column labels of larger tables are 'sticky', and will remain visible when the reader scrolls through a large table, so they can see at a glance what each column contains. Implementation: This is supported natively in CSS by `position:sticky`. However, the naive use of sticky table headers is fragile and runs into many problems (eg disappearing borders <https://stackoverflow.com/questions/50361698/border-style-do-not-work-with-sticky-position-element>, overflows, or _z_-index bugs where the sticky header is *below* table elements). It works mostly in: tables in the base page, not in a collapse, not wider than the page, not in a blockquote, not in popups/popovers, etc. Because of the limited scope & many bugs, the naive approach was not worth implementing: small simple tables don't need it, while the large complex tables that do are relatively rare & would probably trigger bugs. So we implement them in a more complex way to work around bugs. To limit sticky issues, we only do sticky headers on 'large' tables where 'large' > 1 viewport height (ie. a table which would require scrolling). So the table becomes v-scrollable within an inner scroll container (set to be substantially smaller than the window size so there is plenty of room to click on and 'untrap' the mouse), like code-blocks on mobile. Within that scroll container, the headers are sticky. Since they are confined to the inner container and don't need to interact with any other page elements, most of the problems of sticky elements are avoided. Then other issues are dealt with by a bunch of small CSS tweaks.