Daly: Your mum.
Cardy: Your face.
Daly: Your mum's face.
(on NO account bring 'your dad' into this - that's just rude.)
Pat: Your mum's got something on her face.
Percy: okkkk... I havent got anyone to go to Prom with.
Pat: I'm going with your mum.
Percy: stop saying your mum!
Pat: your mum
Percy: your face!
Randomer: Percy dude that was harsh!
Percy: sorry Pat your actually really pretty, will you go to Prom with me?
Pat: I already told you i'm going with your mum!
Teacher: Percy stop talking in my lesson. Whats the answer to question 4?
Percy: Your mum?
Teacher: DETENTION! (note the inappropriate last use here where percy just doesnt know where to stop or how the phrase is used...note Pats master skills FYI she doesnt reall want to go to prom with percys mum duh!)
Your mum originated, presumably, in the UK, which just adds another thing to the list that we'll be embarrased we thought of when we look back at this 10 years from now
Your mum is effectively dead towards punks, grungers, and emos, and ironically has been added to their arsenal of townie impressions.
However, mentioning 'your mum' to a townie or similar missing link of the gene code may result in serious bodily harm, so if you do have to insult them, use words with more than 6 letters to leave them stunned and confused.
B: Fuck your mum
A: You're gay
B: Your mum's gay