1<html><head>
2
3<meta content="text/html; charset=windows-1251" http-equiv="Content-Type">
4<style>
5.d1{position:fixed;top:50%;right:50%;z-index:2;overflow:hidden;}
6.d2{position:fixed;bottom:0;left:0;z-index:2;width:100%;background-color:darkgray;}
7.o {background:green;height:40px;width:200px;}
8.t { width:2000px; height:198px;background-color: lightgray; border: 1px solid blue;}
9body { margin: 0px; }
10</style>
11<script>
12function remove_fixed()
13{
14  document.getElementById("d2").style.position = "static";
15}
16
17function add_fixed()
18{
19  document.getElementById("d2").style.position = "fixed";
20}
21
22</script>
23</head>
24<body>
25<div class="d2" id="d2">This is the parent div.
26<div class="d1" id="d1"><div class="o">This is the nested div.</div></div>
27</div>
28<div class="t">
29000
30</div>
31<div class="t">
32200
33</div>
34<div class="t">
35400<br>
36<button onclick="remove_fixed();">remove fixed</button>
37</div>
38<div class="t">
39600<br>
40<button onclick="add_fixed();">add fixed</button>
41</div>
42<div class="t">
43800
44</div>
45<div class="t">
461000
47</div>
48<div class="t">
491200
50</div>
51<div class="t">
521400
53</div>
54<div class="t">
551600
56</div>
57<div class="t">
581800
59</div>
60<div class="t">
612000
62</div>
63<div class="t">
642200
65</div>
66<div class="t">
672400
68</div>
69<div class="t">
702600
71</div>
72<div class="t">
732800
74</div>
75<div class="t">
763000
77</div>
78<div class="t">
793200
80</div>
81<div class="t">
823400
83</div>
84<div class="t">
853600
86</div>
87<div class="t">
883800
89</div>
90<div class="t">
914000
92</div>
93</body></html>
94