How to show products by product attribute?

Hi,

I am developing locally. At the moment i have two custom product attributes (size and brand).

Now i can display products when i filter on size, like
http://localhost/mysite.com/size/medium
and it shows the products with medium as attri

But
http://localhost/mysite.com/brand/nike
gives a 404

I also tried
http://localhost/mysite.com/?taxonomy=pa_brand&term=nike

What am i overlooking??