Everlasting SEO principles that work, because the web is hypertext
Search Engines are a very significant factor in many businesses today. Many companies will fail or succeed depending on their ranking on Bing, DuckDuckGo or Google. This has understandably created a whole industry of Search Engine Optimisation around it. Money talks.
But it's worth noting that SEO, like programming, isn't a tangible good that you can own - it's free as in experience. You can get far in SEO with common sense and understanding that the nature of hypertext.
Your content needs to be good, trusted and accessible.