What are the Nebraska state laws regarding evictions? Can a landlord give a 3 day notice to a tenant based on alleged contract violations?

Usually three day notices are three day notices of non payment.  As stated from Nebraska legal aid:

"If you receive a 3-day notice of nonpayment of rent from your landlord…

The notice is from the landlord and you need to pay your rent during these three days, but you cannot be put out by the landlord until you are evicted. 

Your landlord may send you a notice in the mail, hand you a notice or leave a notice on your door saying that you have not paid rent for the month and that you have 3 days to pay it.  The notice will usually say that unless you pay the rent in full within 3 days, the lease will be terminated (meaning the lease will end).  You need to pay your rent within these three days.  After the three days are up, the landlord does not have to accept the rent from you, even if you offer the full amount.  Instead, the landlord can sue you for eviction if you do not pay within the three days. The important thing to remember is that this kind of a notice comes from the landlord, not the court, so it does not mean that you need to move out. 

Pay your rent in full plus any late fees within three days. 

If you do this, the landlord must accept the rent and your rental agreement will not be terminated for nonpayment of rent and you will not have to move.  If you only offer to pay part of the rent, your landlord does not have to accept it.

If you cannot pay the rent in full within three days, your landlord might file suit.

            The landlord may file suit asking that you be evicted from the property.  If this happens, you will be served papers by someone from the sheriff’s office or another process server.  See If you have been sued (received papers from the court)… for more information on what to do if you have been sued."

If you feel you have been wrongfully given this notice, contact Nebraska Legal Aid at http://www.nebls.com.