There are several different reasons an extension might not be able to be installed. Most of the reasons usually involve the hosting environment that is set up to support your Joomla application.
Do you want to change the print icons for your articles?
Your template doesn’t match your design expectations?
Do you think tags should look like real tags?
If you asked any of those questions, or even better you have similar concerns about the look of your site, this tutorial is for you.
If you really like a website, I almost bet you the reason is because you enjoy the experience. Besides if it's useful, much better!
That being said, can you mention your favorite sites and why?
If you are not sure what I’m talking about, I’ll give you a few examples so you can apply a similar pattern in your own projects.