HTML was originally designed as a semantic markup language intended for sharing scientific documents and research papers online. However, as the Internet expanded from the academic and research world into the mainstream in the mid-1990s, and became more media oriented, graphic designers sought ways to control the visual appearance of the Web pages presented to end users. To this end, tables and spacers (usually transparent single pixel GIF images with explicitly specified width and height) have been used to create and maintain page layout.
This causes a number of problems. Many Web pages have been designed with tables nested within tables, resulting in large HTML documents which use more bandwidth than documents with simpler formatting. Furthermore, when a table-based layout is linearized, for example when being parsed by a screen reader or a search engine, the resulting order of the content can be somewhat jumbled and confusing.
In the late 1990s the first reasonably powerful WYSIWYG editors arrived on the market, which meant Web designers no longer needed a technical understanding of HTML to build web pages. Such editors indirectly encourage extensive use of nested tables to position design elements. As designers edit their documents in these editors, code is added to the document which is sometimes unnecessary. Furthermore, unskilled designers may use tables more than required when using a WYSIWYG editor. This practice can lead to many tables nested within tables as well as tables with unnecessary rows and columns.
The use of graphic editors with slicing tools that output HTML and images directly also promote poor code with tables often having many rows of 1 pixel height or width. Sometimes many more lines of code are used to render content than the actual content itself.
As the dotcom boom receded in 2001 and the Web development industry shrank, coders with more industry experience were in higher demand. In a large number of cases UI development was carried out by coders with greater knowledge of good coding practice. It was around this time that many became critical of messy coding practices and the idea of tableless design began to grow.
Cascading Style Sheets (CSS) were developed to improve the separation between design and content, and move back towards a semantic organization of content on the Web. The term "tableless design” implies the use of CSS rather than layout tables to position HTML elements on the page. HTML tables still have their legitimate place when presenting out tabular information within web pages.
Read more about this topic: Tableless Web Design