Merged CSS cache not clearing in Magento
In production environment, everyone uses caching. Most of the Magento websites might be having this issue. When you make changes to CSS and you are using the magneto built in CSS merge functionality, you will be pulling your hair with browser cache.
I have experienced the same with Magento, even clearing the browser caching didn’t help me to reflect my CSS changes to a web page.
After searching online I have found out a way, to override the Magento’s Mage_Core_Model_Design_Package Below I have added the changes step by step by creating a module, First of all, we are creating the Magento Module XML file, let Magento know our module is here app/etc/modules/Magrin_Cachefilter.xml
Next we are creating the necessary files for our modules, first is config.xml app/code/local/Magrin/Cachefilter/etc/config.xml
Next step adding the Model file, which override the Magento core model app/code/core/Mage/Core/Model/DesignModel/Design/Package.php app/code/local/Magrin/Cachefilter/Model/Design/Package.php
You may be noticed, Mage::getStoreConfig(‘dev/magrin_cache/cache_string’) in the class this will get you the configuration string from the backend
This is module is built for Magento 1.7 and you can download this module files from Github
Credit goes to following website, for wonderful article,http://smith-web.net/2013/02/09/magento-css-auto-versioning/