In Chrome Developer Tools, there's a section called the "Console" where we can add some Easter egg messages, for example: Welcome to Lan Tian @ Blog. If you can see these lines, then you definitely don't have a girlfriend. These messages can be output using JavaScript with the following implementation code: if ( window . console ){ var cons = console ; if ( cons ){ cons . warn ( '%cWelcome to Lan Tian @ Blog.' , 'color:#09f' ); cons . warn ( 'If you can see these lines,' ); cons . warn ( 'then you definitely don \' t have a girlfriend.' ); } } When cons.warn takes only one parameter, it outputs that sentence in the console. If it takes two parameters and the first parameter (the message) starts with %c , then the second parameter is CSS code. Using cons....