This grammar error only makes itself obvious in the written word, but it does seem to be fairly common.

Use anyone if you can substitute it with anybody.

• Did anyone else hear the news anchor use the slang (read inappropriate) word “diss” this morning? (You could say Did anybody else hear…?)
• Did anyone care? (Did anybody care?)

As far as using any one, it means any single one. Try this: If you can substitute any two, then use any one.

• Did any one of the anchors find it odd to hear a reporter use diss? (You could easily say Did any two of the anchors find it odd?)

The same is true for everyone; it can be substituted with everybody.

• Everyone is here. (Everybody is here.)

Every one means every single one.

• Every one of the guests is here. (Every single one of the guests is here.)

Sherry’s Grammar List

Paul’s book–Literally, the Best Language Book Ever; Sherry’s Grammar List