Of course, tack on the dragonpage dot com part afterwards

I agree with Stackpole that an author creating a world should create their own slang, absolutely!! But, to use some modern slang does not violate any sense of logic or realism–only personal expectations.
Take a look at any English text from 500AD to 1000AD–you won’t be able to read it. (Beowulf in the original English is a good example).
Take any modern fantasy novel and select three sentences. Grab the nouns used and check them out in the Oxford English Dictionary. You’ll find nearly all of them will have entered the English language since 1000AD from French, Latin, a little Norse, a tad of Greek, and a smidgeon of German. Now, if someone says “hell” in a novel you think they better have a hell in their mythos, does that mean if a character says “house” they should also have a Nordic nation in their world? If they say “masonry” they should have a 14th century France in their world? Why should the word “sh-t” be avoided any more if they don’t have a 14th century Germany in their world?

No reason at all, logically, just subjective expectations.