I hope this is the right forum to ask the question, and in any case apologies for the not so "serious" nature of the question!
If you try to validate www.artlebedev.com in the online w3c validator, the validator will show an error <N.B.>Browser is the only validator</N.B.>. I thought it was quite funny and even arguably makes a point, my question though how do they achieve this?
I suspect that they somehow serve a different html page to the validator, which suggests that it is done on the server side, but how would you go about doing this?
Many thanks and sorry again if it is a silly or a beginner question!