Unless the ticket specifically says General Admission or GA, you won't be allowed into certain floor sections.
At the concerts I've been to, they'll typically have sections 1, 2, 3 and 4 (left, right, and center in front of the stage) blocked off from the others. The cut-off point is around half way through the floor.
If it's a sold out show, you're probably pushing your luck finding 3 adjacent seats near any one of your assigned seats. Depending on the night and the security, they tend to enforce the rules on floor seats more so than other higher sections.
You can see the seating chart here:
»www.cheapwholesaleticket ··· hart.gif
Edit: According to ticketmaster, the Killers have a special floor arrangement. The front section is indeed GA. Does your ticket say GA or D, E, F, 1, 2, or 3?
»www.ticketmaster.com/eve ··· catid=60--
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