how to manage a website with 50+ pages?

The simplest method is to use include files and CSS. See http://www.hardcoder.com/scripting/php/include_fil... for info on includes for several platforms.

Beyond that, there is a myriad of choices, ranging from a simple database-driven content lookup page, all the way to a robust content management system (search Google for CMS and you will find thousands of free and paid web CMS products of varying qualities). Many enterprise corporations use very large CMS systems like Microsoft CMS or IBM WebSphere products to manage their site content.

In all, it's a very wide and diverse field. Start with looking into database-driven websites, either using PHP and MySQL or ASP.NET and SQL - the two most common dynamic web development platforms.

You should create a web page with only links. A link on the main webpage should have a link directing user to the links web page.

I really don't understand why you need so many of the same links throughout your site. You should have different links on different pages.

Have you ever tried PHP? Server side includes should make it easy to put a section for the links in each page that you desire, and an update to this section would result in it being viewed on all pages.

The syntax for that would be

<?php require("insertpagenamehere")

?>

Note that the link area has to be in its own file (usually a .php file)

You can use content management system like drupal to manage your site.

No. Sorry buddy.