Every website you visit—including Facebook—is built on layers of code, primarily HTML (HyperText Markup Language), CSS (Cascading Style Sheets), and JavaScript. When you "View Source," you are looking at the raw instructions the website sends to your browser to tell it how to display text, images, and buttons.

Any website or tool claiming to "View Facebook private message source code" is either malware, a phishing scam, or a cookie stealer. Do not enter your password into any third-party "source viewer."

Somewhere in the millions of lines of source code that built the world's social graph, a single line of text remained hidden, a digital fossil waiting for the next archaeologist to dig it up.