Something so small and silly, but that can break a site. I forgot this last week and ran into some trouble. When you’re writing a module file, never put a closing
tag at the end of the file. My editor did this automatically, and I didn’t run into trouble until later, and I realized what the culprit was. A rookie mistake, but easy to make – and luckily, easy to fix. The issue it was causing was adding a blank link to the top of our xml news feed – which caused errors in reading it. The two seemed unrelated, but that was the fix. Deleted the closing tag, and the feed was fine.