This text should appear at the top of the image. This text should appear at the bottom of the image. Notice what's going on in the status bar at the bottom of your browser when you place your mouse over the image. If you are working with a PC, you can easily capture a graphic image from the web by placing your mouse over the graphic, and right clicking the mouse button. Every image is made up of many tiny little dots called pixels.
Pixels are the native unit of measure on the web.
It is a real good idea to note how big your graphics are when you place them on the web page. By adding dimensions, your visitor has something to do while they are waiting for the graphic to load. A word of caution, you also have the ability to skew the size of your image if you don't use the correct dimensions. This is not a good way to scale pictures, because you will lose resolution in the translation, so it's a good idea to keep dimensions 1 to 1. By the way, this might be a very good time to tell you about the alt parameter.