what variable can i use to identify a specific pages i need to load a diff stylesheet depending upon which page the user is on. 

when using: 
     themename_preprocess_page(){kpr(&amp;$variables;)} 

i thought i'd see a pageId or pageTitle in which i could use for a conditional statement but i'm not seeing those variables. am i overlooking something? what can i use to uniquely identify a page so i can the use drupal_add_css()?

i guess i could do at the node level? but the stylesheet i need to load is really a page level thing.

can someone advise on the best way to do? big thanks in advance
You may have trouble adding CSS with drupal_add_css in hook_preprocess_page because the $styles variable has already been built.

Better to add CSS in hook_preprocess_html or hook_page_build

Note, you should be able to target specific pages in CSS by using body classes.

e.g:

body.page-node-type-article #content{
  background-color:pink;
}


But yes, to check the path, you can use 

$arg = arg($index); // system path component
$path = current_path(); // full base system path ($_GET['q']);
$alias = $_SERVER['REQUEST_URI']; // full alias only