When a file is uploaded as part of a form submission, its MIME is included. I've discovered that Firefox on Windows has an inconvenient way of determining this MIME.
The unstyled appearance of the WordPress comment box leaves much to be desired. Some CSS magic can make it look great on mobile and take advantage of available real estate on larger screens.
An introduction to the FileReader interface and where its strengths lie in AJAX file uploads.
A change in Google Fonts' URI structure for embedding combined fonts can lead to an incompatibility with WordPress.
How I resolved an incompatibility between WP Google Maps Pro and Autoptimize plugins preventing maps from initializing correctly.
Create automatically justified horizontal menus with only CSS.