HTML

I have added two HTML tips under the **Style** section.
I agree that using `async` and `defer` is a modern approach and should be preferred. And, regardless to that, I would suggest to put all kinds of `<script>` before the `</body>` anyway. There are my thoughts why:

* If all the `<script>` stays just before the `</body>`, they stay organized right with the non-async and non-defer `<script>` that should be down here anyway. Within this approach they can all stay at one place.

* The `async` and `defer` keywords have full support from IE >= 10. If this support is not an issue, the `<script>` placement can stay untouched when they are at the bottom already.

* If a `<script>` can be deferred, it can also be moved to the bottom of the page. That will make web pages load faster, because of network focus on downloading the `HTML` and `CSS`.
Both `HTML` and `CSS` are **"render blocking"** resources, just like standard `JavaScript`. Resources that may block initial rendering of the page are also called **critical** resources. They are essential when talking about **"optimizing the critical rendering path"** and optimizing the dependency graph between `HTML`, `CSS`, and `JavaScript`.

* Standard `<script>` behaves just like inline `JavaScript`, is **"parser blocking"** and blocks the `DOM` construction. It means that, when the browser encounters a `<script>` in the document it must pause `DOM` construction, hand over the control to the `JavaScript` runtime and let the script execute before proceeding with `DOM` construction.
And why is `JavaScript` a **"parser blocking"** resource? It's because it can modify the `DOM`. But, that's not all. It can modify the `CSSOM` properties too.
And so, `JavaScript` execution is delayed until the `CSSOM` is ready. Thus, the browser will even delay the `<script>` execution until it has finished downloading and constructing the `CSSOM`, and while we're waiting, the `DOM` construction is also blocked!
But, when the standard `<script>` is before the `</body>`, the `DOM` construction remains unblocked to that point, and the `CSS` might be already downloaded in that time.

The benefits seems to be obvious. Although, I do not exclude an option there might be some application specific `<script>` that for some reason does not follow this rules.