Sometimes you want to customize block more then its available through drupal admin, then you start themeing. Quickest way is to copy default block.tpl.php file and then edit its name to something you want to customize. Lets say we customize block number 4, which is block created with views, then you make your file name like "block-block-4.tpl.php" and then change its content. For this to work you have to have block.tpl.php also in your theme folder.
You can dowload php file like that below!