Do spiders spin their webs facing the south
No. Spiders do not build their webs specifically to face south. While some of their webs may face south, spiders are known to spin their webs facing in any direction. Many spiders spin their webs hidden from the prevailing wind, so that the wind won't destroy the web.
In many cases, spiders build their webs based on the nearby environment. For example, some spiders build their nests under rocks or logs. Others may build them in the corner of a room or between branches of a tree. In these cases, direction is not something the spider considers.
It's likely that people came up with the idea that spiders spin their webs facing south based on the direction of the wind in certain areas. Some spiders, such as wolf spiders and jumping spiders, don't spin webs at all. Many spiders, whether they spin webs or not, live in holes or burrows underground.