Width pictures on iPad

As was adviced to me I made the width of the maps here, here and here 900 so it fits nicely in the twenty eleven-theme.

But when I look at my website on an iPad the pictures on those pages are way bigger than the page so it looks like this.

When I check the native pictures they are 900, also the ones uploaded to my FTP are 900. But when I look at the same pictures in my WordPress Dashboard the width is bigger. How can that be? It are al the same pictures?

I hope someone can help so my website will look better on a tablet.

Thanks in advance!