That depends on what the actions are, and what their personality is like.
If someone who wants to
acquire a compact disc (CD) has just sufficient money to buy one, and chooses
CD a instead of CD b, then CD B is the opportunity cost.
To add, opportunity cost. <span>the loss
of potential gain from other alternatives when one alternative is chosen.</span>
HTML isn't really used for this anymore, it's done via CSS (Cascading Style Sheets). On the web currently, HTML pretty much just describes what to be displayed, CSS describes how it's to be displayed and JavaScript is used to provide function to a web page.
In HTML, you could use: align="center" as an attribute of the img tag to center it. Now it's preferable to use text-align: center CSS for the object containing the image (a div or p).
Positioning things on top of each other brings in z-axis and position CSS. Check out the CSS tutorial at http://www.w3schools.com . It's free.
