Another one of Todd and I's back alley discoverys...
The sign says "In dieser Stelle stand bis 1849 das Haus in welcher Mozart am 5. Dezember 1791 gestorben ist"
I can't read the bottom line, but my english translation is "On this spot, until 1849, stood the house in which Mozart died on the fifth of December 1791."
I have to appologise for my translation skills, but I hope you got the gist of it. This is actualy the back window of the largest department store on Kelnerstr. which is aproximately the equivilent of Fifth Ave. for Vienna.