White marks on wood finished tables are caused by hot pots, cups of tea and coffee or pizza boxes. They are commonly known as pizza box marks.
The best solution is to rub with Bri-Wax using super fine (0000) steel wool. Do the entire top starting in one corner and working down the face with the grain. When you reach the white mark concentrate on this area until the white mark has been eliminated and then continue on to the end of the tabletop.
Allow to dry for 2 – 3 minutes and buff with a soft cloth.
Bri-wax comes in many colors. Choose one that best matches your table.