Unfortunately, it's standard protocol to sign away your copyright when you publish in a journal. The language typically allows you to give copies of your article to peers for free if they ask for it, but you cannot give it away freely willy nilly, including publishing it online. The system is really silly. If NIH could facilitate peer review themselves, then we could publish everything in PubMed Central and dispense with journals altogether. They're the Great Satan of science, and they should be abolished. When I write a paper I want everyone to be able to read it whenever the hell they want to. Every other scientist I know feels the same way. For the first time in history the technology to do so is completely trivial, but the backward culture of journals lingers on...