How to disable map introduction screens (MOTD)?
Solution 1:
The command cl_disablehtmlmotd 0 disables MOTD. Goes into the console, but will only work for unofficial servers and not Valve ones.
Solution 2:
You can't.
Source Engine has two types of MOTD: plain text and HTML. If client will choose to disable HTML MOTD, it falls back to plain text.