yairEO's Tagify is a great implementation of a tag component, being very lightweight and using in-built browser behaviour where possible. Here's how I get get suggestions via AJAX rather than a fixed whitelist.

Here's ten things every web developer should be aware of and avoid.

Fixed navbars – that stay at the top of the screen at all times – are common and useful, but sometimes annoying as they can block the top part of the page (sometimes obscuring page anchors).