Are the elements lanthanum and actinium considered to be in the d block or the f block of the periodic table?
Lanthanum and Actinium are generally both accepted as f-block elements. You will notice in the Royal Society's periodic table, La and Ac are both color coded to match the other f-block elements. They do this to show the beginning of both the Lanthanide and Actinide series, while maintaining a reasonable symmetry for their periodic table (that is, without "holes" in their table, similar to the first link you provided).