Optimizing visible text

After web page titles, it's time to optimize "visible text", the second most important criterion for search engines. First of all, let's clearly define what we mean by "visible text":

• The word "text" is used here because what we're talking about in this paragraph is the textual content of your pages. In other words, it's all the content you can select with your mouse, copy and paste into a word processor like Word. In this sense, text embedded in an image is not considered to be in text format. The same applies to text inserted in an animation, etc. ;

• The term "visible" is used here only to refer to text displayed "fairly" on web pages, and does not cover cases of spam where, for example (as was the case over 10 years ago), white text is inserted on a white background, invisible to the surfer but supposedly...