Every wondered how Facebook spoofs Gmail message list snippet text?

Summary

E.g. Gmail inbox shows a message contains "XXX tagged you on Facebook. Take a look about what she said on you."But when you open the message, there's no "Take a look about what she said on you."Answer. The text is present but hidden:<span style=3D"color:#FFFFFF;font-size:1px;opacity:0;">Take a look at what she said about you.</span>And unsurprisingly whenever I do click through, I find she hasn't said anything about me.