I (indirectly) use HTML, but instead of writing straight in HTML, I write with Markdown which is text formatting language that Stack Exchange uses (you wrote your question with markdown, I'm wrote this answer with markdown, etc).
You can make links, bold, italics, lists, insert images, etc.
So far, my answer looks like this:
Similar to what [Philip](https://worldbuilding.stackexchange.com/a/19598/9708) said:
I (indirectly) use HTML, but instead of writing straight in HTML, I write with [Markdown](https://en.wikipedia.org/wiki/Markdown) which is the text formatting language that Stack Exchange uses (you wrote your question with markdown, I'm wrote this answer with markdown, etc).
You can make [links](https://worldbuilding.stackexchange.com/questions/19594/organizing-lore), **bold**, *italics*, lists, insert images, etc.
This is quite readable even if you don't know the syntax.
Similar to what Philip said:
An old fashioned HTML/Markdown index could link to different sections of lore.
For my story, I have separate sections for alien creatures, alien cultures, things happening on Earth, etc. You should have top headings, ("Alien cultures") with subheadings that have a short description and link to more complete information:
Your index might look like this:
- Prefer to eat spicy food.
- Think 'guacamole' is inherently funny
- Enjoy abducting cows
- Sworn enemies of the Foobarians
- Refer to their warriors as 'the Barbazians'
- Insectoids from a very hot planet
- Master swordsman, fearless explorer
- Hapless and surrounded by incomprehensible alien tech.
etc, etc. Each link should take you to more detailed information. The character links for example, might link to a mini-biography, description and selection of quotes.
(Click edit if you want to see how I made that list)
The index can link to more detailed lists, as well, depending on the size of your world. A section titled "Alien Tech" might link to sub lists entitled "Games", "Faster than Light", "Communication", etc. For a fantasy world, replace "Tech" with "Magic", etc.
This makes for easy cross-referencing, which is as simple as linking to the right page.
Can I try Markdown
Sure, markdown is free. You will want to ask on another StackExchange for detailed installation instructions, but it should be as simple as installing perl and downloading markdown.