alternar = true

var todos = []
for ( i = 0; i < linhas; ++i ) todos[ i ] = i

var actual = [ 0, 1, 2 ]

function alternaDestaques(){
   if ( !document.getElementById ) return

   var novos = todos.slice()
   var pos = -1
   for ( i = 0; i < 3; ++i ){
      while ( pos < 0 || pos >= novos.length )
         pos = Math.ceil( Math.random() * novos.length ) - 1
      document.getElementById( "imovel___" + actual[ i ] ).style.display = "none"
      actual[ i ] = novos[ pos ]
      document.getElementById( "imovel___" + actual[ i ] ).style.display = "block"
      novos.splice( pos, 1 )
   }
}