There is, however, old wisdom — perhaps from an earlier version of the Mac HIG — that says how to create error messages: they should be of the form “Can’t x because of y.”

They may optionally include additional detail and/or recovery steps. “Can’t x because of y. Something is true. Try a thing.”

A similar form is this: “Noun can’t x because y.” (As in “‘’ can’t be opened because it is from an unidentified developer.”)

One thing error messages [ never say ]{style=“color: #ff0000;”} is [ sorry ]{style=“color: #ff0000;”} . (…)

Also: they rarely (if ever) use the words [ I, me, my, you, and your ]{style=“color: #ff0000;”} .

(via inessential: Error Messages )