I am familiar with Contemplate module, and also the option of having node.tpl files.
But, how could I alter node content via node api programmatically? I would like to add some custom HTML. Any tips?
i think you are looking for hook_nodeapi functionality which provides possibility to add additional content along with node content.
ex; adds a variable to node which is also available to display in node template
function test_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {
switch ($op) {
case 'view':
$node->content['var1'] ='<div>test value</div>';
break;
}
}