Everyone will agree that in places where there is a lot of text to read it is important to make the experience as comfortable as possible. Just such a place is a webpage or email newsletter. Two important aspects affecting readability are line spacing and contrast.
Before CSS was supported in web browsers the ability to control line spacing was a vital feature missing from HTML. Unfortunately email clients haven't caught up with the CSS support people enjoy in their web browser, and so care should be given to ensure the email is readable.
When there is little or no space between lines of text, it becomes intimidating and difficult to read. For comfortable reading, a line of text should be about 40 to 60 characters, or eight to ten words. Lines that are longer than ideal are also tiring and the beginning of the next line down becomes more difficult to locate.
Lines that are too
the eye's left to right
to be disrupted
Many early Web pages had text running all the way from the left side of the screen to the right, regardless of the screen size. Many newsletter messages still do – and screens have become wider too.
The way the eye views words on a printed page and a computer screen is different. A printed page is viewed with reflected light, while a page on a computer screen is luminous. This makes the difference between black text and a white background many magnitudes greater on a monitor than on a printed page.
Reducing the contrast of Web page text makes for more comfortable, less stressful reading. If you go too far however, you start to make things difficult for people with poor vision. Some experts will recommend having a gentle background tint and soft colors, while others will insist that plain black and white text is preferred. A fun tool to view the difference in readability between text and background can be found here.
Other General Readability Tips
A serif font is easier to read in hard-copy print and a sans serif font is easier to read online. If you were wondering, serifs are the little marks at the end of letters. Sans serif fonts do not have serifs. Examples of serif fonts are Times New Roman and Courier New. Popular sans-serif fonts are Arial and Verdana.
- White space, even on the most content-rich emails, can keep text areas clean and contained.
- Keep the number of fonts and styles limited to only two or three. If you don't have branded guidelines that detail typefaces or if you haven't modified these for email, you should.
- Not every picture needs a frame. Borders can enhance an image, but they can also stop the eye along its natural scanning path. You can ruin a good design with to many frames and boxes.
- Plain text is easier to read than italicized text, as I hope this example illustrates.
I hope that you can use some of these tips to make your newsletters as readable as possible.