When reading some of Salvatores books I noticed this was spelt diffrently. In Servant of the Shard its Lolth, and in The Thousand Orcs its Lloth. Since it was spelled Lolth in IWD2 is Lloth just some error?

It may just be a typeO. Have you taken the time to read on and see if it is spelled the same in the rest of the book?

Unless there is a repeating typo in the City of the Spider Queen Web Enhancement, it's Lolth .

In Homeland the drow say it Lloth, the sverfneblin call her Lolth.

Both spellings are used just about as often, and they're both for the same thing, so in descriptions it's often noted as Lolth/Lloth.

Though afaik, Lloth is used only in Menzoberranzan and and Uluitur, so you often see this alias in Salvatore's books.