The grammar site that I found helpful was "A Guide to Grammar and Writing."  The site is super easy to navigate, and allows you to pick the part of a sentence or writing that you have a question about, and it breaks it down into fairly simple terms.  You might have to look past the '90s web design madness, but after ignoring the background and horrible table outlines, it's actually pretty helpful.

This week's editing error brought to you by Instagram.

While I absolutely adore the boots, and I'm impressed that her 12-year-old helped her pick them out, her caption is filled with mistakes!  Hyphens missing and "but" instead of "buy" (though I'm cutting her a little slack there because it came from a phone.  Autocorrect is a pain!).  However, if you want your hashtags to work correctly, please spell "heels" correctly.  No one looking for pictures of high heels will search "heals."  I promise.