Every state has different laws regarding adverse possession. You need to discuss your particular situation with an attorney. In general, the five elements that must be met to have a claim of adverse possession are that the possession are as follows:
1. Open and notorious. Your possession must be in a manner that is overt (done right out in the open), not covert. Your possession must be seen. That gives the owner notice that you are in possession and the opportunity to eject you.
2. Actual and uninterrupted. That means that you actually have possession and control over the land in question, without the owner's consent, and that possession is not only occasional.
3. Exclusive. You are the exclusive possessor and actually entered the property for the required period of possession which varies in different jurisdictions.
4. Hostile. That means that you treat the land in question as your own against the rights of the legal owner. Adverse possession is not created when you have the permission of the landowner to use his land (so a long-term tenant cannot claim adverse possession).
5. Made under a claim based in good faith. Those seeking equity must do equity. So if you acted in bad faith somehow, your claim would be barred. For example, moving the fence to a position where you knew it didn't belong would be considered bad faith.
You must have met all five of these elements to qualify for adverse possession. You have the burden of proving you met each element. You must have met these elements for the statutory period required in your state. In most states your title would need to be perfected by a court action.
If you believe that you have a claim of adverse possession, or are facing an adverse possession lawsuit, you should see a real estate attorney immediately! Adverse possession is a complicated subject, and you don't want to take it on without the guidance of a qualified counselor at law. To find an attorney in your area, look in your local phone book.