This is a base HTML file without BS5 that validates.
Added the necessary link and script tags to the document head to tap into the BS5 ecosystem. Notice the difference between the 2 files, especially how some of the default HTML styling has been removed (margins/padding) and the change of font family.
Provided these elements:
onload and onresize actionsgetElementByIdvisually-hidden BS5 classtext-shadow to obey the 'C'ontrast principle from the CRAP ruleinput element of type="button" to toggle back and forth between 2 different styles. Use JavaScript to change the href property of the developer linkimportant! CSS designator to override BS5 class styles (::hover style to allow underlining on hovering)Evolution Upgrades:
h1 and h3 to work as a unitheader elementindex3.html Upgrades:
header area to a BS5 design