I was not previously aware of iBase. On quick review of its home page as well as the links provided by matthew589, it appears to be a high quality resource, based in the UK. However, it is designed primarily for HIV infected people with questions about treatment and living with HIV/AIDS, not those who have been exposed and are concerned about becoming infected. Still, it has accurate information about how HIV is transmitted -- and most important for many users of this forum, how it is NOT transmitted, e.g. by kissing, body contact, exposure to most body fluids, and so on.
It's an interesting site. Not sure I agree with it all. For example, it says 95% for 4th gen test at 4 weeks.
I've heard that exact number for 3rd gen tests.
And if 95% was the number for 4th gen test, as it says,
why would UK, many states in the US now, many other countries in South America consider it conclusive at 4 weeks? Even the CDC has (according to AIDSMAP) said its good after 4 weeks.
But it does seem to have some other good information.