The stylings applied are slightly different. You should look at the source and see what styles have been applied. For instance id="ImageGalleryStyle". In the CSS you should then style this accordingly.
You might want to consider something like Firefox's 'Firebug' which will help you debug the CSS (switch it to DOM mode and click on the element you want to style).
This is not something that is SilverStripe specific AFAIK.