If you are running Joomla then you will be using a joomla template for your site which makes use of the template_css.css file to control the layout of your web site, modules, components and more. In some cases the template_css.css file can grow pretty big and have an impact on your page loading time plus hosting resources.

I found a very useful article called PHP_CSS_Compressor written by ibloomstudios who have come up with a simple but effective solutions for automatically compressing your CSS style sheet using a few lines of code which can be included in your design.

For more information read the PHP Compressor Article.