There is a certain wifi network that am around a lot. It is very slow and pretty much unusable. I would rather just never see it. As it is, it pops up every time asking me to join. Is there a way that I can have that particular network only never ask again.
The only way to do this would be to set "Ask to Join Networks" [sic] to OFF in your iPhone wifi settings.
I find this to be preferable. The main consequence is that, when you are in some place new, you'll have to manually select an available wifi network. But once you HAVE joined a network, it'll automatically join it when next available. And (more germane to your question) it WON'T ever join a network that you haven't explicitly joined.