You tell him means &ldquo;I agree wholeheartedly with you have just told him and support you unreservedly in expressing it frankly, to his face.&rdquo;

What does "You tell him!" mean?
I am learning VHDL from zero using Altera CPLD. Already got Quartis II 12.1 and a 15-lines example VHDL (like Hello World for C learner). 

To avoid learning bad coding style or digging too deep too early, what should I look out for?
