401 error on new laptop

I have a new computer been having problems with staying connected to internet. loaded new 8.201 connections. PER HP still happening.. I go to a page then hit go back to main page then I get a message internet not found. I have to click on the back button then hit it again. I did up grades to firefox and all up grades to computer.

<!-- Error Title -->
<div xmlns="http://www.w3.org/1999/xhtml" id="errorTitle">
<h1 id="errorTitleText">Server not found</h1>
</div>

<!-- LONG CONTENT (the section most likely to require scrolling) -->
<div xmlns="http://www.w3.org/1999/xhtml" id="errorLongContent">

<!-- Short Description -->
<div id="errorShortDesc">
<p id="errorShortDescText">Firefox can't find the server at www.facebook.com.</p>
</div>

<!-- Long Description (Note: See netError.dtd for used XHTML tags) -->
<div id="errorLongDesc">
<ul>
<li>Check the address for typing errors such as
<strong>ww</strong>.example.com instead of
<strong>www</strong>.example.com</li>
<li>If you are unable to load any pages, check your computer's network
connection.</li>
<li>If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.</li>
</ul>
</div>

<!-- Override section - For ssl errors only. Removed on init for other
error types. -->

</div>

<!-- Retry Button -->
<button xmlns="http://www.w3.org/1999/xhtml" id="errorTryAgain" autocomplete="off" onclick="retryThis(this);" autofocus="true">Try Again</button>
<script xmlns="http://www.w3.org/1999/xhtml">
// Only do autofocus if we're the toplevel frame; otherwise we
// don't want to call attention to ourselves! The key part is
// that autofocus happens on insertion into the tree, so we
// can remove the button, add @autofocus, and reinsert the
// button.
if (window.top == window) {
var button = document.getElementById("errorTryAgain");
var nextSibling = button.nextSibling;
var parent = button.parentNode;
parent.removeChild(button);
button.setAttribute("autofocus", "true");
parent.insertBefore(button, nextSibling);
}
</script>

this is what im getting everytime I try to go to a page