Glass is not a high-viscosity liquid at room temperature: it is an amorphous solid, although it does have some chemical properties normally associated with liquids. Panes of stained glass windows often have thicker glass at the bottom than at the top, and this has been cited as an example of the slow flow of glass over centuries. However, this unevenness is due to the window manufacturing processes used in earlier eras, which produced glass panes that were unevenly thick at the time of their installation. It is common to find old windows which are thicker at the sides or the top.
Wikipedia has a pretty good list of Common Misconceptions, with references explaining why they aren’t true, and what the real story is. Unlearning a wrong fact is one of the hardest things to do as a human being, so do yourself a favor and unlearn something wrong today.