<em> and <strong> have always been there as long as I recall, and are part of the 1995 HTML 2.0 spec. Before NCSA Mosaic, your hypertext was being rendered on t

<em> and <strong> have always been there as long as I recall, and are part of the 1995 HTML 2.0 spec. Before NCSA Mosaic, your hypertext was being rendered on text based terminals. Most of them couldn't render italics, and for emphasis tended to invert foreground and background, use underlining, or color if you were lucky. The use of italics and bold to add emphasis started when people started using the first WYSIWYG HTML editors in the later 90s. People who had never learned HTML or even written hypertext before, concerned primarily with making things pretty. And this problem drove the creation of CSS, to get people to stop using tables for layout but never quite got people to understand <i> and <b> were exclusionary, except at the Universities where they had to support braille terminals and screen readers for visually impaired students.