Adverse Possession 
If you can prove that you have been in occupation of someone else's land for the necessary length of time set out in your state’s applicable legislation then you can acquire rights of possession in the land.
In Victoria after 15 years, the true owner's title is barred and if you can show 30 years of adverse possession then you may be able to have the full title in the property transferred to you provided you are able to satisfy the Titles Office with proofs of your occupancy over that period or assignment of any possessionary rights from the previous owner to you. This process is called Adverse Possession.
The context that Adverse Possession usually arises is when fences are not located on the true title boundary. The best means of clarifying any irregularity is obtain a survey plan from a registered surveyor. If the amount of land enclosed by a fence on the wrong alignment is only small then you may simply decide to leave the fence where it is. However where the area of land enclosed is more substantial then this may have a significant bearing –positive or negative- on the value of your property. In these circumstances you should seek immediate legal advice.