$(document).ready(function(){
  var windowWidth = $(window).width();
  var contentWidth = $('#wrapper').width();
  var bgleftWidth = $('#bg_left').width();
  var bgrightWidth = $('#bg_right').width();
  
  if(windowWidth <= (contentWidth + bgleftWidth + bgrightWidth)){
    $('#bg_right').css('left', (contentWidth + (windowWidth - contentWidth)/2)+'px');
    
    if(windowWidth <= (contentWidth + (bgleftWidth)*2)){
      $('#bg_left').css('left', (windowWidth - contentWidth - (bgleftWidth)*2)/2+'px');
    }
  } else {
    $('#bg_right').css('left', (windowWidth - bgrightWidth)+'px');
    $('#bg_left').css('left', '0px');
  }
  
  $(window).resize(function(){
    var windowWidth = $(window).width();
    var contentWidth = $('#wrapper').width();
    var bgleftWidth = $('#bg_left').width();
    var bgrightWidth = $('#bg_right').width();
    
    console.log(windowWidth);
    
    if(windowWidth <= (contentWidth + bgleftWidth + bgrightWidth)){
      $('#bg_right').css('left', (contentWidth + (windowWidth - contentWidth)/2)+'px');
      
      if(windowWidth <= (contentWidth + (bgleftWidth)*2)){
        $('#bg_left').css('left', (windowWidth - contentWidth - (bgleftWidth)*2)/2+'px');
      }
    } else {
      $('#bg_right').css('left', (windowWidth - bgrightWidth)+'px');
      $('#bg_left').css('left', '0px');
    }
  });
});