Added alt tag

This now conforms to standards complience

qrcode.js

@@ -361,6 +361,7 @@ var QRCode;
 			this._oContext = this._elCanvas.getContext("2d");
 			this._bIsPainted = false;
 			this._elImage = document.createElement("img");
+			this._elImage.alt = "Scan me!";
 			this._elImage.style.display = "none";
 			this._el.appendChild(this._elImage);
 			this._bSupportDataURI = null;