Long ago, in a terminal far, far away...
The first public mention of HTML was in the year 1991 as Tim Berners-Lee described the 18 tags that were initially available in the markup language. It was 1994 when a working group was established for HTML - The Internet Engineering Task Force (IEFT). They believed the web belonged to the people (an idea that still holds strong today, especially with the battles over net neutrality), and so their doors were open to anyone who wished to join. By the year 1995 we were graced with many new tags and attributes, such as being able to set the font and background colour. This drew some criticism as the argument was that HTML should only be used for describing the structure of a document, and not for styling which went outside the scope of this. At this time, browser vendors were tearing ahead of the HTML working group, and finding consensus on new features came very slowly. To tackle this, the vendors came together to dedicate themselves to standardising HTML, and a month later the HTML working group was disbanded due to it's slow-moving nature.
Ever remember slicing up a PSD, then firing up Dreamweaver to create a table to hold all those images? It's something we wouldn't dream of doing today, but oh how we still yearn for that level of simplicity. We've come a long way when looking at HTML 5. It no longer refers to just the tags, but also an API that lets us grab information such as geolocation, or a device's battery level. It's important to keep an eye on your own battery level when keeping up to date as well.
It wasn't long ago that all our styles were usually confined to a single CSS file.
We'd construct styles without giving them too much thought compared to the specificity minefield we know it as today. Sass (Syntactically Awesome Stylesheets) arrived in 2006, but it wasn't until a few years later when methodologies like OOCSS (Object-Oriented CSS) really took hold of the web for scalable, maintainable and re-usable styles. Nowadays we may use naming methodologies such as BEM (Block, Element, Modifier), or SUIT CSS, but what results is good old CSS in the browser. What's coming in the future looks promising with CSS variables, and hopefully element queries.
It's really hard to describe the future, because as soon as there's a whisper of a feature someone, somewhere, will have found a way for us all to use it. It's the blessing and the curse of working on the web. Whatever technology comes around the bend doesn't negate what you already know, so keep learning and adapting.