If you want to "Play" with making code changes you can use the "inspect" feature that most browsers have available.
Do a right mouse click on any page and locate "inspect" in the drop down. It will show you the coding for the entire page you are viewing. If you want to see a specific area you can right mouse click on that area and view the coding for that specific area.
Now for the fun part. You can edit the code that is displayed (change colors, names etc etc) and it will change the look of the page. When you leave the page it will revert back to the default. So you can play all you want!!!
