So far, it looks good with helpful information: from the site:
"This index includes 427 references to both the Guide to grammar and Writing and Principles of composition."
For example of part of an entry on the passive voice:
Verbs are also said to be either active (The executive committee approved the new policy) or passive (The new policy was approved by the executive committee) in voice. In the active voice, the subject and verb relationship is straightforward: the subject is a be-er or a do-er and the verb moves the sentence along. In the passive voice, the subject of the sentence is neither a do-er or a be-er, but is acted upon by some other agent or by something unnamed (The new policy was approved). Computerized grammar checkers can pick out a passive voice construction from miles away and ask you to revise it to a more active construction. There is nothing inherently wrong with the passive voice, but if you can say the same thing in the active mode, do so (see exceptions below). Your text will have more pizzazz as a result, since passive verb constructions tend to lie about in their pajamas and avoid actual work.