This page is a work in progress.
In the beginning, HTML and its predecessor Gopher were so simple that their very nature influenced the style of web pages.
Over time, more and more artsy-fartsy and pointy-haired-bosses demanded "style". They kept messing with web pages to try to make them work more like magazine pages. But back then things were so simple that this wasn't possible without lots of images and a hellish amount of complex "scripting" (to use that word very loosely). Using images was a very bad idea, because broadband internet was nearly unheard of. Yeah, everyone was on dialup.
But over time, web browsers started bringing in non-standard features to the net. Microsoft made a very heavy push towards taking over the web standards. They introduced a whole lot of quirks into Internet Explorer and many many people leveraged them to make their site "better".
The reason that Internet Explorer and other web browsers started making their own non-standard features is that critical decisions on the nature of the net and its standards were still being expanded and agreed upon. By the time the standards overtook the non-standard functionality given by the web browsers, many websites were already built using those non-standard features. Some pages and even entire sites were quite broken depending on what web browser and what version of what web browser you used. Even when the standards were improved, there was a lot of confusion among web developers on the right way to make any given web page.
But that's the past. These days the standards have overtaken many of those old quirks. Web developers, web development tools and web browsers have all been greatly improved. Things are looking good.
There are still some remaining items like vector drawn graphics and rounded corners which aren't browser-supported.
- Vector graphics is generally drawn with the proprietary Adobe SVG plugin but it's also being worked on by the Mozilla SVG Project for native Mozilla-browser support.
All in all, much more functionality has been given to developers so that they can make web pages look however they like.
But the problem has always been that while the developer should offer a pleasing default style, the user should be the one deciding on their preferred style.
It's possible for a developer to create alternate stylesheets. This website uses them. This is a decent start, but picky users or users with whatever personal tastes and needs will want to take that styling power away from the website and the web browser developers.
Firefox has two extensions which allow the user to customise the content of any web page:
-  Stylish
-  Greasemonkey