If the contract is to your satisfaction, put your signature and date on the line marked by the X.

No, you can put an X or an arrow or a little sticky tag that says "Sign Here" or any other indication that a signature is required. If you're asking if the "X" mark constitutes a valid signature, the answer is "probably", but only if it was made with the intent to be a signature on the document.

The Xs under a signature represent kisses. Some people add Os, which represent hugs.

25 cents

The X is actually the Greek Letter Chi, which is a symbol for Christ. When the X was originally used in the signature field, it meant, "I promise in the name of Christ".