>to allow for viewing on any browser and on any platform
[ranting response]
shona, this is because there was/is no standard for the way that HTML is *interpreted*. this is supremely stupid, but there IS a putative standard for writing HTML, but as a web publisher I have absolutely no guarantee as to how different browsers will "read" my pages. this is a swell thing for the writers of "web pages for dummies" and the like...
[/ranting response off]

my calmer self will now step to the fore and tell you that most "amateur" publishers will, in an attempt to maintain their readers (and sanity), limit themselves to verifying their own pages with the major browsers (e.g., IE, Netscape, perhaps AOL (ha!)).