to keep track of all of these in my personal css framework, i made an entry in the base stylesheet for every html element, even including a couple deprecated bu

to keep track of all of these in my personal css framework, i made an entry in the base stylesheet for every html element, even including a couple deprecated but widely supported ones (i also keep a list of fully deprecated elements in comments), though not every element gets styled beyond the default. meter/progress can be styled consistently, but it's tricky because of the browser inconsistencies you mention. it took a lot of playing around with weird vendor-prefixed pseudos to get these looking similar across platforms. sub/sub/abbr just need to be normalized first - normalize.css is a good reference for this. abbr can be useful for providing short "aside" info on a word/phrase in a semantic way. styling detail/summary is relatively easy and they're pretty useful for FAQs and the like. i see web designers experimenting with more and more these days. map/area, i don't use, but have seen it used on experimental designs to neat effect. and object is as you said, hard to predict for styling. ps - it looks like chrome (105) will finally support mathML along with firefox and safari, so perhaps that will impact sub/sup usage in the future.