One of the first things that I learned when writing code was to copyright it. As far as I know, the things to do are:

1. Create a license file that describes the copyright and lists the software files.

2. Add the copyright to each file containing code. Ex: # (C) Copyright <years> <name>. <license>.

3. [Optional] Register the software into official organizations of intellectual property.

the stages 1) and 2) I've always seen it in heavy client software, but I ignore why big corporations like Facebook, Google, Microsoft, etc... never do it in their web code (speaking about step 2). And they also don't even use the HTML meta tags:

<meta name="author" content="">
<meta name="copyright" content="">

Is there any legal reason behind this? Is their code already declared on step 3 so they don't bother doing step 2?