$(document).ready(function() {

  $("#buscadorgoogle").focus(function() {
    $("#buscadorgoogle").css("background-image", "url(../images/bg_input.gif)");
  });

  $("#buscadorgoogle").blur(function() {
    if($("#buscadorgoogle").val() == ''){
      $("#buscadorgoogle").css("background-image", "url(../images/bg_input-google.gif)");
    }
  });

});