Real World: I wanted to make an expanding, adjustable, rounded corner, complicated module. I didn't want to just add some nice border to the module. I wanted fancy.
Easier said than done. But it can be done. Here's how.
I'm going to use the basis of another tutorial. You can access that other tutorial at WebDesignerWall, here. But I'll tell you what you need to know from that tutorial now. You can download my image files here, and it will eventually look like this.
Step 1: Make a box you want on the site! See my tutorial.
( How to design my own module in Joomla.)
Step 2: Go into your administrator back-end, Extensions>Module Manager, and set-up a module (New module -->Custom HTML -->Enable). Under PARAMETERS on the right of the module set-up, you will notice a box called "suffix." Type in the name of your module design you will code. In other words, if your module will be called "bird," in the suffix box put underscore bird or _bird, no spaces.

For our purposes, the module will be called "sunbox." This is how the module parameters would look for this exercise: