/**
 * Preprocess variables for page.tpl.php
 */
function modulename_preprocess_page(&$vars) {

  // Customizations for all User/profile paths.
  if (arg(0) == 'user') {
    // Do something
  }

  // Customize Login page.
  if (arg(0) == 'user' && (arg(1) == 'login' || !arg(1))) {
    $vars['title'] = 'Log in';
  }

  // Customize Register page.
  if (arg(0) == 'user' && arg(1) == 'register') {
    $vars['title'] = 'Create a new account';
  }

  // Customize Request Password page.
  if (arg(0) == 'user' && arg(1) == 'password') {
    $vars['title'] = 'Forgot your password?';
  }

} // End preprocess_page.