Creating the site with the Amiga is not a problem. Viewing it, however, may be. It is possible to make a site that looks fairly decent that is viewable on the Amiga as well as other places but it must be done using older website building techniques (ala without much or any JavaScript and little to no CSS).
That, of course, really limits modern web design in a big way. I just say this because it's what I do for a living. If you have a powerful enough Amiga, you can run things like NetSurf which will get you half way there with CSS support, but that browser has some serious issues in and of itself.
So short answer is yes. Long answer is above.