<style>
    div { float:left; margin:5px; }
    .head { width:50px;height:50px;background-color:pink; }
    .info { width:250px;height:200px;background-color:blue;display:none; }
</style>
<div>
  <div class="head"></div>
  <div class="info"></div>
</div>

window.onload =function(){
    var oHead = document.getElementsByClassName("head")[0];
    var oInfo = document.getElementsByClassName("info")[0];
    var timer = null;
    oHead.onmouseover=function(){
      clearTimeout(timer);
      oInfo.style.display="block";
    };
    oHead.onmouseout=function(){
      timer = setTimeout(function(){
        oInfo.style.display="none";
      },500);
    };
    oInfo.onmouseover=function(){
      clearTimeout(timer);
      oInfo.style.display="block";
    };
    oInfo.onmouseout=function(){
      timer = setTimeout(function(){
        oInfo.style.display="none";
      },500);
    };
};

oInfo.onmouseover = oHead.onmouseover=function(){
  clearTimeout(timer);
  oInfo.style.display="block";
};
oInfo.onmouseout = oHead.onmouseout=function(){
  timer = setTimeout(function(){
    oInfo.style.display="none";
  },500);
};

window.onload =function(){
  var oHead = document.getElementsByClassName("head")[0];
  var oInfo = document.getElementsByClassName("info")[0];
  reminder(oHead,oInfo,"onmouseover","onmouseout");
  function reminder (div1,div2,event1,event2){
    var timer = null;
    div1[event1] = div2[event1]=function(){
     clearTimeout(timer);
     div2.style.display="block";
    };
    div1[event2] = div2[event2]=function(){
     timer = setTimeout(function(){
      div2.style.display="none";
     },500);
    };
  }
};

window.onload =function(){
  var number=0;
  reminder("head","info","onmouseover","onmouseout",number);
  function reminder (div1,div2,event1,event2,num){
    var oHead = document.getElementsByClassName(div1)[num];
    var oInfo = document.getElementsByClassName(div2)[num];
    var timer = null;
    oHead[event1] = oInfo[event1]=function(){
     clearTimeout(timer);
     oInfo.style.display="block";
    };
    oHead[event2] = oInfo[event2]=function(){
     timer = setTimeout(function(){
      oInfo.style.display="none";
     },500);
    };
  }
};

var number=null;
for(number=0;number<3;number++){
   reminder("head","info","onmouseover","onmouseout",number);
}