Prestashop is caching *.tpl files, so after any change, you need to delete cache to apply these changes.
A) You can delete cache by deleting all files in /tools/smarty/compile/
B) In Prestashop administration (Preferences > Image): Turn off caching and turn on force compile in BO > Preferences > Performance and then just reload the page. Make sure to setup it back after reloading page, it is important for performance.
Prestashop 1.5 already recompiles template files automatically (with default setup). You can also clear the cache manually via administration. Go to Advanced parameters > Performance and click on "Clear Smarty cache & Autoload cache".
2. Issues with displaying page in Internet Explorer
3. Enable debug mode
Prestashop 1.4 - 1.5.2
edit config/config.inc.php and change these two lines to be as follow:
/* Debug only */ @ini_set('display_errors', 'on'); define('_PS_DEBUG_SQL_', true);
Prestashop since 1.5.3
edit config/defines.inc.php /* Debug only */ define('_PS_MODE_DEV_', true);
4. How to change logo to png format
Go to Preferences > Images and setup > Image quality > setup "Use PNG only if the base image is in PNG format".