The information that follows was extracted from an earlier version of the Lower Austrian State Archives (NÖLA) website, but I can no longer locate a link to this on their new site.
Austria before 1918 means the Habsburg Empire. The Habsburg Empire was called the Austrian Empire from 1804 onwards. The Austrian Empire became the Austro-Hungarian Empire in 1867. So if your ancestors stated "Austria" as their nation of origin, they did not necessarily come from within the boundaries of modern Austria. They came from the Habsburg Empire, a multi-national, multi-ethnic conglomerate. The following list gives you the political entities which made up the Habsburg Empire. The modern states which evolved out of these political entities of the Habsburg Empire are added in the third column: