> developers needed a way to explicitly tell the browser to open the link in a new tab, free of frame semantics First, it doesn't say why an underscore does that, because you could totally have underscores in frame names. My guess as others here is that the underscore prefix dates back from reserved names in C and C++. IIRC the reserved names also included "_self" (even if it was the default), "_parent" (to go up a l…
Technically, the underscore was restricted and should not be used for user defined targets/frame names. This isn't something any browser I know of ever enforced.