Nth change after modify template theme file

I download and install a theme and want to test it by modify the code in the php and css file.
css files has no problem (it can immediately show me the change after refresh the webpage)

But the template theme file has nth change.
The downloaded theme has a "page.tpl.php" in its folder (it override the default one).

I remove part of the code as show below:

            <?php if ($logo): ?>
            <a href="<?php print check_url($front_page); ?>" title="<?php print t('Home'); ?>">
            <img src="<?php print $logo; ?>" alt="<?php print t('Home'); ?>" />
            </a>
            <?php endif; ?>

After remove those code, I suppose the logo image should be gone. But after refresh the webpage. It still exist.
I have try to click "Clear all caches" in Drupal Configuration, and even restart apache. But there's still nth change.