lovers of typography love a well designed ligature. those who are indifferent to typography generally say “what’s a ligature?”. and those who are entirely ignorant don’t even notice a ligature even when they are looking straight at one. although, that’s actually the point of the ligature in the first place — you’re not supposed to notice the typographic trick, because the ligature is intended to make reading easier.

just to make clear the foregoing blather — here are some standard ligatures in well-known fonts. you’ll notice that not all fonts have been designed with a full complement of ligatures :

that’s right, ligatures are those little joined-together thingies that are generated by default in InDesign. unfortunately, ligatures do not always lead to improved readability and sometimes you’re better off just using the standard letterforms.

you can turn ligatures off in the dropdown menu in the character panel. if you’re doing the right thing and using styles for your text formatting, you’ll find ligatures as one of the options under basic character formats. you can set no-ligatures as your default for all future documents by unchecking it in the character panel when you have no documents open.

the only way to turn ligatures off for an entire document in one hit is with a script something like this one :

tell application "Adobe InDesign CS4"
  tell active document
    tell every story
      set ligatures to false
    end tell
  end tell
end tell

of course, the Adobe CS being what it is, you do NOT turn ligatures off in Illustrator the same way you do in InDesign. for Illustrator you have to go to the opentype panel instead.