Help with Adding Links!

Hello,

I’m creating my own WordPress theme from scratch using Adobe Dreamweaver, and having a heck of a time adding links to my index.php page. My site is designed with a header, footer, a left sidebar and a right sidebar, each with their own respective php files all of which work fine on the main index.php file. My left sidebar is simply an unordered list with various site navigation links. My site is currently set on a local server. When I test the index.php page on the server it looks as it should in addition to “test” clicking the links in the left sidebar. However, when I click the back button, or my “home” button (which simply links the user back to index.php) I get the following error message:
Fatal error: Call to undefined function bloginfo() (then it continues with the file and line of code).
I’m not sure what this means at all or how to fix it. The line of code the error references is as follows:
<link rel="stylesheet" type="text/css" media="all" href="<?php bloginfo('stylesheet_directory'); ?>/style.css">
However, what’s weird is that when I remove this code and simply use a standard call for the css page, such as <link href="style.css" rel="stylesheet" type="text/css" /> the test page on my server will end up picking up a difference error, for example: Fatal error: Call to undefined function get_header().
What does this mean and how can I fix it?
Thanks again!!