Yasmin asked a question in a previous comment regarding the word "herbal". She observed, "... this always irritates me when I hear it, in Britain we always say "Herbal" and when I hear people from the US it always sounds like "Erbal or Erbs why is the H silent but in spelling the H is always used, or is it just a slang that's used?"
Good question. First of all I looked up the word "herb" in my Oxford English Dictionary of Etymology, 1966. On page 437 it says, in part, "The sp. [spelling] with h is recorded from the earliest times, but the pronounc. [pronunciation] without initial aspirate was regular till early XVI." So at least as early as the 16th century the silent "h" was common.
Why is the "h" silent? The American Standard Dictionary of the English Language Fourth Edition, 2000, makes this interesting usage note: "The word herb, which can be pronounced with or without the (h), is one of a number of words borrowed into English from French. The (h) sound had been lost in Latin and was not pronounced in French or the other Romance languages, which are descended from Latin, although it was retained in the spelling of some words. In both Old and Middle English, however, h was generally pronounced, as in the native English words happy and hot. Through the influence of spelling, then, the h came to be pronounced in most words borrowed from French, such as haste and hostel. In a few other words borrowed from French the h has remained silent, as in honor, honest, hour, and heir. And in another small group of French loan words, including herb, humble, human, and humor, the h may or may not be pronounced depending on the dialect of English. In British English, herb and its derivatives, such as herbaceous, herbal, herbicide, and herbivore, are pronounced with h. In American English, herb and herbal are more often pronounced without the h, while the opposite is true of herbaceous, herbicide, and herbivore, which are more often pronounced with the h."
So apparently either is as acceptable as the other. It always sounds strange to me to hear the "h" pronounced in herb (unless the Herb being pronounced is short for Herbert). On the other hand, my mother has always pronounced the word "humble" as "'humble" with a silent "h", and that used to bug me no end! But according to that usage note, it is acceptable either way! I also found a reference that said it was more common in the South for the "h" to be silent in the word "humble", so perhaps that was something my mother got from her Virginia grandparents.
I hope this answers the question.