a.htm:
<button onClick="newwin1=open('b.htm','newwin1','')">open newwin1</button>
<button onClick="newwin1.newwin2.close()">close newwin2</button>b.htm:
<button onClick="newwin2=open('c.htm','newwin2','')">open new win2</button>
<button onClick="newwin1=open('b.htm','newwin1','')">open newwin1</button>
<button onClick="newwin1.newwin2.close()">close newwin2</button>b.htm:
<button onClick="newwin2=open('c.htm','newwin2','')">open new win2</button>
var b=window.open("b.htm")
c.close()
b.htm
var c=window.open("c.htm")