www.apastyle.org--American Psychological Association "A Complete Resource for Writing and Publishing in the Social and Behavioral Sciences" (There is a version available for Kindle).
I'm not sure why they chose to suggest that style guide, though: I would have chosen the ubiquitous Chicago Manual of Style, used by book publishers, since most of us aren't writing in the social or behavioral sciences on HubPages.
I could even see choosing the AP Style Guide (Associated Press), which is for journalists, though again most of us aren't writing news articles we're writing fiction, poetry, how-to/DIY, poems, etc. etc. and not reporting on time-critical current news.
There is a specific online style guide I recommend and use when Chicago is silent on a subject: The Yahoo Online Style Guide (or something close to that): very comprehensive with lots of relatively up-to-date information about social media (which is instantly outdated, now, of course).
For the best little style guide, I always recommend Strunk & White's Elements of Style. You can read it cover-to-cover in a few hours, it's informative and not preachy, sometimes even amusing, and something I recommend that all writers and editors read at least once a year no matter how good they think they are. :-)