firebug

>>Right click in the white space on this page and click “view source” and look at the HTML.

Most people think of HTML when they consider programming for the internet.  Many other languages are used (Java, SQL, HTML5, Flash, …)
If you were going to make a website you would probably just use a template and an online wizard.  But it can be handy to know some basic HTML when you have to make a few tweaks (or want to include content in a post).

>> Go to www.purple.com and then press F12 on your keyboard
Press F12 on other pages and play around.