The problem is: "Determine whether the relation R on the set of all Web pages is reflexive, symmetric, antisymmetric, and/or transitive, where(a, b)∈R if and only if

a) everyone who has visited Web page a has also visited

Web page b.

I can see how it is transitive--it is always true that someone who visited webpage a also visited webpage a, or in ordered pair notation, (a, a).

What I am having difficulty seeing is how it is not symmetric. Wouldn't it be true that, if you visited webpage a, then you visited webpage b, could be stated as, if you visited webpage b, then you visited webpage a? Meaning that (a, b) and (b, a) are elements of R?