They're some ad from some mobile company and other sponsors.
I was up there once in summer. Whoah it was pretty scary. I mean it wasn't if you weren't afraid of heights. It was going very very slow for it is for city sightseeing. The longer we stayed higher, the more afraid I was. Ahh silly me, I wasn't even able to make pictures of beautiful scenery below.
Check out more signs on the link below:
