A few years ago I decided that whenever I solve an issue like this I should make a note somewhere of the issue and solution for future reference. Initially I did that in an APEX application I built at my place of work - in fact I intended to share it with other developers, though no one else really bothered with it. It was a kind of in-house developer forum with one user, me.
The downside of that was that I could only access the information from my place of work, and when I moved to another employer I had to leave it behind. I considered moving it to APEX on the cloud somewhere, but by then I'd started using Trello for managing my workload on different projects, both work and personal. Trello is really simple and effective: rather than describe it here I'll point to their own board basics page. Also it's cloud-based so I can access it from anywhere. I realised it would work rather nicely for my personal "knowledge base". So I created a new board called "QandA". It looks like this:
The board consists of three lists:
The Solved list obviously contains issues that I have previously solved - this is the real "knowledge base". The Unsolved list is stuff I'm currently solving or will need to solve. The Help/About list is just some brief help in the unlikely event that I forgot how to use the board.
When I hit a new issue I add a card to the Unsolved list, with a title describing the problem e..g. "How to #toggle an #img #icon using just #css". I've been using hashtags like that to aid future searching a bit (and anyway you have to have hashtags everywhere these days anyway don't you?)
When I find out something about the solution to the problem I update the card and add the new information. This can be a comment, a link to a web site, a picture, a Word document attachment or whatever. Some things I add may be potential solutions that I haven't got time to check out right now.
Eventually, the problem is solved (hopefully) and then I drag and drop the card to the Solved list, and perhaps edit it to remove potential solutions I had noted but didn't work. My knowledge repository has grown bigger.
OK now some months later I hit an issue with jQuery in Internet Explorer (of course) and I think I've solved it before. So I open up my Trello board and filter using the relevant keywords:
In the solved list I can now see just the 4 cards that have both #ie and #jquery in them somewhere. I see the card I'm interested in, open it up and I have the solution. Lots of time saved!
TL;DR: use Trello, it's great!