2.4 Omit Closing Tags

The trick here is to omit any unnecessary closing tags. This means omitting </li>, </p>, and removing the self-closing slash from tags like <br /> and <img />

Warning: this tip will make your HTML invalid, and you run the very real risk of weird rendering. Most browsers will let you get away with unended </li> tags, but a missing </div> will often break your page layout.