code: function() {
  		if ( !( this.header[0] === 0x4e && // 'N'
  		        this.header[1] === 0x45 && // 'E'
  		        this.header[2] === 0x53 && // 'S'
  		        this.header[3] === 0x1a // ending character
  		)) {
  			throw new Error("Invalid ROM!");
  		}
  		
  		if ( this.header[7] & 0xe ) {
  			throw new Error("Bit 1-3 of byte 7 in ROM header must all be zeroes!");
  		}
  		
  		if ( this.header[9] & 0xfe ) {
  			throw new Error("Bit 1-7 of byte 9 in header must all be zeroes!");
  		}
  		
  		var i;
  		for ( i=10; i <= 15; i++ ) {
  			if ( this.header[i] ) {
  				throw new Error("Byte " + i + " in ROM header must be zero.");
  			}
  		}
  		
  		if ( this.header[6] & 0x4 ) {
  			// TODO support trainers
  			throw new Error("Trained ROMs are not supported");
  		}
  	}
docs: Validate INES header.
  Throws an exception if invalid.