IS ALL MARGARINE VEGAN?
Nope. A lot of margarine brands use whey (milk solids) and other dairy ingredients. Check the label to be sure.
CAN I USE THE "SPREAD" KIND THAT COMES IN A TUB?
Unless you're buttering your toast, it's not recommended. Spreads contain more water than the kind that comes in stick form, so it could throw off the chemistry of the recipe, particularly when baking.
WHERE DO I FIND VEGAN MARGARINE?
Some vegan margarines can be found in conventional grocery stores, but be sure to read the ingredients. Your best bet is a natural foods store. Earth Balance is a popular brand.