A bit of a blurry photo, but looks good for the Mussing Sector Orb Web spider, Zygiella x-notata.
This is a very common and widespread species and is commonly mistaken for Steatoda nobilis, the Noble False Widow. These spiders love to make their webs over windows and use the corners if the frame and the sill for its refuge. I doubt there is a home in the land that does not have this species in residence.
They are completely harmless and through the year they will catch a good deal of insects and other invertebrates that are considered pests. They are also one of the few species that happily feed through the winter given available winter insects.