line length, white space, justification & hyphen-ation
Wednesday, November 12th, 2008introduction
The way in which people read text has been extensively studied since the 19th century, yet when one looks for definitive information on choosing an appropriate line-length for a website for optimum legibility, a wide range of conclusions is found. Recent experiments have shown that on-screen reading speed increases with longer line lengths (testing in the range 35 – 95 characters per line). Other experiments have shown that line length had little effect on readability, but that readability was substantially affected by the size of the surrounding white-space margins, with large margins substantially enhancing readability. Another recent experiment showed that margins slow reading speed, but increase comprehension. These studies are not necessarily conflicting; taken together they indicate that line length itself is not as key as might have been thought, but providing adequate white-space margins (which, coincidentally, will somewhat decrease line length) is important to comprehension, which is even more important to a commercial website than reading speed.
My local newspaper (The Age) uses a principal layout comprising eight columns, each only 45 mm. wide, which results in 28 – 34 characters per line – so short that, in combination with the fact that the text is justified, about 15% of lines end in a hyphen.
Unlike a newspaper or magazine, which has a set size combined with a set font and font size, the website visitor has a high degree of control over properly-designed websites and can change the overall size, text size, font size and even font family. This degree of flexibility more or less rules out hyphenation of text, which, in contrast with newspapers and magazines means that very narrow columns work less well.
Justification (i.e. where inter-word padding is inserted to make all lines equal in measured length) is the rule rather than the exception in books, magazines and newspapers, but the exception rather than the rule on websites. Justification looks much better when combined with hyphenation, and is therefore less appropriate for websites. In addition, only a limited range of browsers support justification.
techniques
The simplest and cleanest way to ensure that you have adequate white-space margins around text is to set the margins directly in CSS e.g.
margin-left: 15%;
margin-right: 15%
etc.
Note that it is preferable to set these margins as percentages of the available width (rather than absolute values) so that they adjust appropriately when the page is resized. Most websites will, however, be more complex in their layout and we must also bear in mind that “white-space” is not necessarily unoccupied.
Setting CSS to justify text (text-align: justify;) or to right-justify text (text-align: right;) works with Mozilla Firefox 2.0.0.13 and its cousin Netscape Navigator 8.0.4. With Internet Explorer 6.0.28
or Opera 9.27, these justifications can be made to work, but the inheritance mechanism in their CSS implementations is not correct and so each element that is to be justified (other than the default ‘left’) has to have the justification specifically set i.e.
body {text-align: justify;}
may not be sufficient, you may need, for example,
body {text-align: justify;}
td {text-align: justify;}
to reliably achieve the justification.
This article is an extract from the “Saffron Book” (Good Practice for Commercial Website Design) available for on-line purchase at e-books.