Adding tooltips or hover text to Blogger posts and gadgets

This article is about putting a "tooltip" (text that is shown when you hover over) into something (eg text, a web-address or even a picture) in a Blogger post or gadget. What are tooltips? Tooltips are a feature found in many websites and modern computer based software: when a viewer hovers their mouse over an item, a small piece of text is shown, generally formatted in a box which is highlighted in some way. They can be used for all sorts of things, to provide definitions of technical or foreign-language words, additional information about particularly interesting concepts - or as an incentive or invitation to take an action eg you could tool-tip "click here to enter" with a description of the prize or benefits of entering.) You can see them in Blogger's Post Editor when you put your mouse over an item in the toolbar. But tool-tips can be used on other things too, including pictures and text: put your mouse over This Text to see one. They can be particularly...