I have definitely seen the number of websites Firefox can't load correctly
increase as all other web browsers shift to Webkit or similar rendering
engines. I think a lot of sites are just not bothering to test for Firefox
anymore or something.
I use Lynx as a secondary browser and generally it does a good job of just
getting me to the text I want to read, but not all javascript forms and such
work.
As time has gone on I have increasingly been preferring sites and services
that minimize the use of anything beyond html/css or use the simplest
features beyond them. When I am thinking of purveying a new site or service,
I actually first visit it in Lynx to see how well it functions. If it does
well, then I use my main browser.
Website bloat is a real problem, designers have gotten so lazy it is
maddening. I choose to withhold my site hits for sites actually designed well
with respect at their core.
