HL2 Riddle

Go to half-life2.com and visit the Media page. Move your mouse over the pictures until one turns into a picture of the G-man and click it.

Type 'nova' for user and 'prospekt' for password. View the source of that web page (View > Source). Scroll to the bottom of the source code and copy the web address. Add this copied address to the end of the 'half-life2.com' web address and hit enter. Now you will see a picture of a barnacle. Go back to the black web page with the white box and type in 'barnacle' in the empty field.

Enjoy :)