There's a tendency in this liquid language of ours to stick words together. I remember being in grade 2 and hearing Mrs Alderton tell us about compound words: two words which, when placed together, form a single, new word with a new meaning. I can still remember knowing what a fish was and what a wife was, but having no idea what the result of putting these two words meant. Come to think of it, I still have no idea what a fishwife is, though I'm pretty sure it's a real word and not just my grade 2 memory playing tricks on me. I must remind myself to look that up next time I'm thumbing through my New Shorter Oxford. Whatever one is, I can't imagine they'd be any good in bed.
However, people often get confused about whether they should be stringing as many words together as their handwriting will allow, or whether the space bar should be employed to full effect.
One (or two, or in fact, three) such word(s) that is (are) all-too-often misused and confused for one or the other combination of one- or two-wordedness is the addition of the words every and day, forming the new word everyday.
Used separately, the words every day refer to exactly what they say they refer to, namely, every 24-hour period of your (or everyone's) life. For example, a student might say "I go to school every day," even if, as is usually the case, they don't actually go every single day (unless they're particularly diligent, or dumb, in which case you might find them swotting in the library on weekends).
When we put the two words together, however, we get an entirely different meaning (not to mention an entirely different type of word: separately, they are an adjective and noun respectively but together they form a single adjective). Everyday means ordinary, or commonplace (and while it can mean 'occuring every day', I'm going to conveniently ignore that usage for now because it'll only confuse things). Everyday is an adjective you would use to describe something normal, or uneventful.
So, my bank offers everyday banking accounts. These are good for day-to-day banking; deposit here, withdrawal there. Basic stuff. However, my phone company's flier, containing an offer for me to have "a different photograph on your handset everyday" belongs in the same rubbish bin as those home-made leaflets that come through the letterbox that employ clip art and Comic Sans in their design and expect to be taken seriously. I'm not taking the telephone people up on that badly worded offer. No thanks, you illiterate multi-national greedbag. Go back to school, or hire a proper writer.