Scroll bars

We did specify that slot A1 should only use 200 pixels (in terms of its height). However, the problem is that the content overﬂowed the height! This is a simple problem to ﬁx, as we can specify the overflow property.

Listing 6:

overﬂow

1<!DOCTYPE HTML PUBLIC ”−//W3C/DTD_HTML_4.01//EN”

2  ”http://www.w3.org/TR/html4/strict.dtd”>
3<html lang=”en”>
4  <head>
5    <title>An illustration of CSS−based Layout</title>
6    <style type=”text/css”>
7      div.slotA {
8        position: relative;
9        background: red;
10      }
11      div.slotA1 {
12        position: relative;
13        height: 200px;
14        overflow: auto;
15        background: green;
16      }
17      div.slotA1 > div.slotB {
18        position: absolute;
19        width: 20%;
20        background: yellow;
21      }
22      div.slotA1 > div.slotC {
23        position: absolute;
24        left: 20%;
25        width: 80%;
26        background: gray;
27      }
28      div.slotD {
29        position: relative;
30        background: purple;
31      }
32    </style>
33  </head>
34  <body>
35    <div class=slotA>
36      Red stuff represents slot A. Slot A is the title portion of a document.
37      It spans 100% of the width, and is as high as it needs to be.
38    </div>
39    <div class=slotA1>
40      <p>What is this green stuff? This is slot A1. Slot A1 includes
41      slot B and slot C.
42      However, this portion does not belong to either one. Slot A1 includes
43      both the main content and a left bar for navigation links.</p>
44
45      <p>Note that we have to set a height for this slot because it contains
46      slot B and slot C, which are block that have absolute positions.</p>
47
48      <p>The entire slot A1 (including slot B and slot C) share the height
49      of the slot A1. If the content is taller, then a scroll bar is usually
50      rendered to scroll through this block.</p>
51      <div class=slotB>
52        <p>˜Slot B is colored yellow. Its width is 20% of the containing
53        block ”SlotA1”.
54        This portion is normally used to include navigation links.</p>
55      </div>
56      <div class=slotC>
57        <p>Slot C is colored gray. This is usually where the main content goes.
58        Its
59        position uses slot A1 as the frame of reference. We need to specify
60        the left to be 20% because that part is used by the slot B.
61        The width of the slot is 80% because 20% of the full width of
62        slot A1 is already used for slot B.</p>
63      </div>
64    </div>
65    <div class=slotD>
66      This is slot D (purple). This slot is usually reserved for copyright
67      notice and a email link to the webmaster.
68    </div>
69  <body>
70</html>

Line 14 in listing 6 shows that we can specify the handling of overﬂow to be auto. On most browsers, this means the automatic use of a scroll bar. The rendering of this code is shown in ﬁgure 4.

Ah, this is much better. You can try to resize the browser, and visualize how the various blocks will be resized.

3.3.5 Scroll bars