Determine the likely size of your Web page by looking at the widest table that will print on a standard letter-size page, which is 535 pixels. Ideally, limit the text line length on a Web page to 10-12 words per line. Margins define the reading area of your page by separating the main text from non-text elements. Use table cells to establish margins, and use them consistently throughout your site to provide unity. Web audiences tend to be diverse, and from a readability standpoint, all information must be clear and concise.
Web users have short attention spans.
A Web visitor expects to find a specific unit of relevant information - not a book. Text design includes font, style, size and color. The following considerations are general guidelines for Web page use. Sans serif fonts are best suited for titles, headers, and labels because they are easily recognized and understood. Serif fonts are more suited for body text because they are easier to read for extended time periods.