How to remove validation on zip code in magento checkout page

In the World some of the country has no zip code like Ireland, But magento has default zip code validation to make that optional for specific country magento has added a new feature in admin panel. To make Zip code optional please follow the following steps.

Login to your your magento admin panel then go to System -> Configuration->General. From Country option tab you can see there is an option " Postal code is optional for the following countries " Select the country which you want to Optional/Not validate . then click on save config to save your settings. To be more clear on this please see the below screenshot.