@media only screen 
   {
   .m1_box__50__01 {display: block;}
   .m2_box__50__01 {display: none;}
   .m3_box__50__01 {display: none;}
   }
@media only screen and (max-width: 800px) 
   {
   .m1_box__50__01 {display: none;}
   .m2_box__50__01 {display: block;}
   .m3_box__50__01 {display: none;}
   }
@media only screen and (max-width: 500px) 
   {
   .m1_box__50__01 {display: none;}
   .m2_box__50__01 {display: none;}
   .m3_box__50__01 {display: block;}
   }