Leicester University: Richard Mobbs' "Introduction to HTML/XHTML: Tables"
Tables are used on the Web in much the same way that they are used in word processing: to present tabular data. This use-case is extremely helpful for users, as it makes information easy to locate and see. In this chapter, Mobbs notes that tables can also be used to structure the elements of a webpage, since you can include images, paragraphs, and many other elements inside each cell. Generally speaking, this is a use-case for tables that has been superseded by the use of CSS to position and organize content and should be avoided. In conceptual terms, the reason for this is that using tables to organize content is effectively a use of HTML for presentational information - which is CSS's job. Instead, tables should be used for semantic information - that is, to designate a part of an HTML file as tabular data, rather than to specify how that data is presented. That said, in some Content Management Systems, tables may be the only convenient way to organize content in an HTML file. In these cases, using tables to organize content is fine.