Just got through watching “Midnight Mary” on TCM starring a young Loretta Young, and noticed something I have seen in old movies a couple of times before- “to-day” instead of “today” in ads, as in “no jobs to-day”. Why was this done? Was it common? Why/when did it fall out of favor?
Very common. The general evolution of the word was from “to day” to “to-day” to “today.” The OED doesn’t have exact dates, but by the 19th century “to-day” seems to be the common form, with “today” taking over in the 20th (there are also some exceptions – the path wasn’t smooth).
The English language has a general tendency to shorten phrases and then to place their component parts next to one another. Connecting them with a hyphen follows, and time and familiarity gradually erodes the hyphen. Modern usage is similar but faster. E.g., electronic mail - e-mail - email.
Today is really a compound word, shortening the expression to the day.
The Online Etymology Dictionary says of today:
Tomorrow is quite similar:
Some 19th century prose looks today as if it were composed by a drunken computer typesetting system, Take this line from Twain’s intro to Huck Finn:
The use of the hyphen remained standard in formal English later than the early 20th century, as later quotes even for to-day and to-morrow are easy to find. Probably it wasn’t until after WWII that standards relaxed and the removal of hyphens became the norm.
I am a great believer in trying to preserve what is proper and correct English usage. At the same time, I strongly favor saving keystrokes, so long ago I went from “e-mail” to “email,” etc.
Oddly, on those rare occasions when I write on, what do you call it, oh yeah, paper, with a pen, I tend to avoid the shortcuts. See what computers have done to us? 
I’m a good Canadian, so I try to avoid dropping the hyphen in “e-mail” to preclude confusion with “enamel.”
Unless, of course, you spell it “e-namel.”
That should be namel, eh? 
I find myself instinctively typing “e-mail”, backspacing to remove the hyphen. I’ve used email since 1987, back in the days when it was really called “electronic mail,” so I’m more familiar with the hyphenated name.
I still find myself using “the Web” or “the WWW” instead of “the web” - the lowercase “web” seems to be the norm now.
Anyghow, back on topic. I’ve seen lots of old references to “base-ball”, but not “foot-ball” or “basket-ball.” Were the hyphens ever used in what is now called “football” and “basketball?” What about terms that really didn’t come into usage after WWII, like “freeway” and “expressway” - were they ever “free-way” and “express-way?”