<?php print $site_name; ?>
Why I couldn't perform the above code in 'html.tpl.php'. This works find in page template. Please suggest how to load this in html template
There's no $site_name
variable added to html.tpl.php, but you can add it yourself quite easily with a preprocess hook:
function MYTHEME_preprocess_html(&$vars) {
$vars['site_name'] = variable_get('site_name', 'Default');
}