To re-learn math, both websites and books provide visual content (text and some of them shows illustrations). So are websites an alternative to books (content quality-wise)?
My goal is to re-learn from pre-algebra (I'm that behind). I feel like I don't remember details about what I learned in school, but as soon as I read it, I will understand it easily, because I have the synapses, but they are missing lots of links.
I want to know if websites can provide me >= quality content as books. I want to be sure that my knowledge doesn't have any holes on it so I can go to advanced concepts without that fear of not understanding something because of incomplete basic knowledge.
I think your question is very general. If you want to advance your knowledge I would say first go over basic math skills - that is material learnt in algebra, precalculus and geometry courses. For this I would highly recommend the Khan Academy. Of course you should also find exercises in books or whatever other content you have to apply the skills you learn since the best way, I feel, to understand a concept is to see an application of it in another pretext.
For more advanced mathematics I think finding texts from universities around the world is very helpful, though of course a general background is necessary. If you have a concept you are interested in Id recommend reading about it in a specific book and finding info on the web (the more versions of a concept the better) and practicing it through university exercises that you can find on the web.
Hope this helps somewhat..