http://www.luminous-lint.com/app/iframe/photographer/Frantisek__Drtikol/primepositionseo.com/2021/05/29/rwfeds/

This is display.cgi (source). It takes some text you enter into a form, and displays it for you as HTML. This is a great way to see how some HTML code looks in your (or someone else's) browser. So paste 'n go: