can you really make money on EBAY or having your own store online?

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I have a website and now that i got it up and running i am finding out i need to know how to submit metatags(HUH?)and alot of other things i have no idea what i am doing. I tried listing some of the items with EBAY and that fell apart I almost sold an item for less than what i have to pay i had to cancel that and now I am afraid to even list anything because now I am owing 25 dollars to ebay. What am i doing wrong and is there really oppertunities to make money on ebay? is there anyone else experiencing success on ebay that would care to share some advice or any suggestions as to what I can do to get my store listed in a better position?