Improve accessibility with keyboard navigation
That "the website is usable for users who use a keyboard and not a mouse" is the second requirement on Digitaliseringsstyrelsens list on web accessibility.
Code
Articles containing CSS, HTML, PHP or .htaccess code snippets that you can either use as is, or use for inspiration in your own projects.
Mark external links and PDF files with CSS
It's a boost to the usability of your website when you clearly indicate that a link leads out of the site or to a PDF file.
Strengthen the security of websites with HTTP Security Headers 2023
Securing websites is tricky, and it may be hard to see what you're gaining from the effort. But if your site is compromised, you risk harming both your company's reputation and ranking in search results. Updated with deprecation of Expect-CT og X XSS-Protection