content is centered after trying a widget

hi there,

I made a simple site for my dad’s coocking-club http://eetkluppie.nl

Everything was going well and i was almost finished with it…

But after i tried to add an archive-widget in the content-sidebar, but deleted immediately because it didn’t do what i expected of it. All my contend was centered after the widget try-out, and the featured images in some posts are suddenly very big!

Now i’v read there a some plugins for these errors, but this is a site hosted by wordpress (or how do you call it when the site is not on a self-hosted server)

hope someone could help me i would appreciate it very much.