$(function() {
    $('#propertythumbs>img').each(function() {
        $(this).css({ 'cursor': 'pointer' })
               .mouseover(changeSrc);
    });
});

function changeSrc(event) {
    var src = $(this).attr('src');
    $('#propertyphoto>img').animate({ 'opacity': 0 }, 300, function() { $('#propertyphoto>img').attr('src', src).animate({ 'opacity': 1 }, 300); });
}