To inculde a css file to your site add a link tag in the <head> section of your page, for javascript add a script tag.
<head>
<link href="file.css" type="text/css" /> // This wil include your css file
// For JavaScript
<script src="jquery.js" type="text/javascript" ></script> // This wil include your java script file
<script type="text/javascript" >
// write Your JavaScript code here
// For using jquery code, add jquery method inside the script tag, example below
$("document").ready( {
// your jquery code
});
</script>
</head>
Script manager is used for different purposes:
1) Using Ajax Controls
2) When we access web services in Client Side
3) Page Methods etc
From MSDN about ScriptManager:
You must use a ScriptManager control on a page to enable the following Microsoft Ajax features of ASP.NET:
Client-script functionality of the Microsoft Ajax Library, and any custom script that you want to send to the browser. For more information, see Creating Custom Client Script by Using the Microsoft Ajax Library.
Partial-page rendering, which enables regions on the page to be independently refreshed without a postback. The ASP.NET UpdatePanel, UpdateProgress, and Timer controls require a ScriptManager control in order to support partial-page rendering.
JavaScript proxy classes for Web services, which enable you to use client script to access Web services and specially marked methods in ASP.NET pages. It does this by exposing the Web services and page methods as strongly typed objects.
JavaScript classes to access ASP.NET authentication, profile, and roles application services.