Gravatar always shows default image

Question

When I call the following code:

echo get_avatar(
    get_the_author_meta('user_email'), 
    '70', 
    get_bloginfo('template_directory')."/images/default.png"
);

It generates the following:

[http://1.gravatar.com/avatar/f456a030d4086504d0796f0134139410?s=70&d=http%3A%2F%2Fblogs.com%2Fscience-and-medical%2Fwp-content%2Fthemes%2FBlog%2Fimages%2Fdefault.png%3Fs%3D70&r=G][1]

It is adding to the end of the default URL:

%3Fs%3D70

This prevents it from working and always returns the default image. If you remove the extra data from the URL it works.

Answer 1

I worked out I needed to add quotes around the parameter.

echo get_avatar(get_the_author_meta('user_email'), '70', "'" . get_bloginfo('template_directory')."/images/default.png'");