No, that wasn’t a HTML error (authough it could become one if the title is blank). That, was the most useful tag you will ever use.
I am partly writing this for my own use as when I edit my websites I almost always forget this tag. All it does (if you know HTML you already know that this is anti-climax of the year) is add a blank line. Two create a paragraph gap. But, and stay with me here, think how many times that tag is used in a single web page. Now think about if they weren’t there (obviously it would only affect sections of plain text but the point still stands).
I also know that any web savvy people like myself are yelling at their screens (probably not … That would be wierd) what about <div>, <span> and of course the ones that actually make a web page load like <HTML>, <head>, <body> and <style>. But these are obvious, they need to be there and as such become habit. I would be willing to bet that 80% of people who write in HTML on a regular basis start with:
And fill in the rest of the tags from there, I know I do. The same applies for the other tags displayed above, they are used so often they become habit, an almost automatic “I need text. I need <div>” reflex, whereas <br> while being very important, is not (in my case at least) is not used often enough to be added to autopilot mode. So in conclusion, <br>, the unsung hero of HTML.