Some sites have "don't be scared" text, which some users might actually read. For instance: "Once you push this button, you will have another chance to review your order before it is submitted". Or when appropriate, a "be scared" warning: "Once you push this button, your order will be submitted, and it cannot be cancelled".
If you are targeting older users, keep in mind that many of them are accustomed to reading text, and would prefer a couple of explanatory sentences to a semi-mysterious icon.
If you are targeting older users, keep in mind that many of them are accustomed to reading text, and would prefer a couple of explanatory sentences to a semi-mysterious icon.