Prueba

<p style="text-align: center;"><a href="http://vanillaandcookiescupcake.blogspot.com/"><img src="http://i49.tinypic.com/9fs6sl.jpg" alt="Vanilla and Cookies Cupcake" onmouseover="this.src='http://i48.tinypic.com/11rx0qv.jpg';" onmouseout="this.src='http://i49.tinypic.com/9fs6sl.jpg';" style="border: 0pt none ;" border="0" /></a></p>