[xp84]

My first time wading into web development was hopping into the source of the MSN.com homepage circa 2000 to see how their DHTML menu rollovers worked, and then stealing it. It was mostly CSS, but to support some browsers they had JS assist with what's being moused over.

That kind of thing is utterly impossible to replicate with a modern frontend build -- all the classes are generated by styled components and all the behaviors are attached with React or Angular. Best you could hope for is to find some telltale attribute that points you toward an open-source library. Or, hope they left their sourcemaps on.