unable to add w3.org icon on ssl https site

Hi,
We tried to add your w3.org icon to our site https://soescrow.com to show our users that our site is compliant http://jigsaw.w3.org/css-validator/validator?uri=http://soescrow.com&profile=css21&usermedium=all&warning=1&lang=en, but the icon does not show when it is https://soescrow.com pages. Why? We tried to modify your url by adding https, but it did not work.
How can we add w3.org icon to a ssl https website?
Regards
Pierre
http://soescrow.com