Are you concerned about what your guests will wear to your wedding? Since you can't go to their homes and pick out their clothes, give them some clues to help ensure that everyone is dressed appropriately.
If you want all the men in tuxedos and women in evening gowns, then have "black tie" or "formal attire" printed on the lower corner of your invitation. If you want your guests to be formal but don't need to have everyone in a tux, then print "black tie optional." If you're not sure attire wording will fit on the invite, talk to your stationer about your layout and insert options. You can have a separate card inserted with your invitation that reads:
Dinner and dancing to follow
Your guests will know how to dress themselves, and of all the details you need to tend to, worrying about their wardrobe should not be one of them. There are certain attire rules that most, if not all, people will follow:
Saturday (or Sunday) night after 6 p.m.: formal/black tie
Daytime weddings: suits for men and cocktail dresses for women
If you're concerned about a handful of guests, you can either tell them (or have someone else tell them) what's appropriate or just let them come as they are and don't think about it. A guest that is dressed inappropriately will be more embarrassed for himself or herself and you probably won't notice, because you'll be too busy enjoying the day.