style=site is the default site style; it's the same as style=mine *for me* because I use that one. AFAIK there is no way to force it for LJ, which drives me bonkers. (Besides, LJ's scrambled their code so that all the features no longer work with the default site style.) (I avoid reading posts on LJ; I can't comment there with my browser of choice because of the scrambled code problems.) When I did linkspam roundups, I set the LJs to ?format=light and the DWs to ?style=site.

?style=mine gets the journal style of the reader if they're logged in. I think it gets nothing if they're not; it gets whatever the default page setting is.

Tumblr is full of pr0n. I am stunned that it's not blocked on my work computers. (I gather that the IT/security department hasn't quite noticed the existence of tumblr. That, or they think McAfee is all the websecurity they could possibly need, so why bother having filters on top of it?)