What is the simplified form of 1/2/3/4

1/24?
or 3/8

your form is ambiguous, you will need brackets

e.g. it could be (1/2)/(3/4), then the answer is
(1/2)*(4/3) = 4/6 = 2/3

following the strict rules of BEDMAS, since all operators are the same we have to perform the operations from left to right in the order they come
so 1/2/3/4
= (1/2)÷3/4
= (1/6) ÷ 4
= 1 /24

Wolfram followed that method:
http://www.wolframalpha.com/input/?i=1%2F2%2F3%2F4