NullReferenceException: Object...

I recently created a dreamweaver site as a way to get my portfolio out to potentiel employers/clients.?It's a simple site with a download button that links to a PDF file created in Indesign.?The Site is hosted by GoDaddy.?90% of the time everything functions great, but occasionally, I Get the following error when trying to click the button:

[NullReferenceException: Object reference not set to an instance of an object.]
IIS7Injector.InjectedContentStream.Write(Byte[] buffer, Int32 offset, Int32 count) +135
System.Web.HttpWriter.FilterIntegrated(Boolean finalFiltering, IIS7WorkerRequest wr) +281
System.Web.HttpResponse.FilterOutput() +119
System.Web.CallFilterExecutionStep.System.Web.HttpApplication.IExecutionStep.Ex ecute() +47
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean%26amp; completedSynchronously) +75

I've also noticed that the ''up'', ''down'', and ''over'' buttons don't display the way they were set up, which is not a big deal, but I thought it may be related to the null error.?My Code can be found below, the site is http://nightskymediadesigns.com , any assitance would be greatly appreciated.?THANKS!

%26lt;!DOCTYPE html PUBLIC ''-//W3C//DTD XHTML 1.0 Transitional//EN'' ''http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd''%26gt;
%26lt;html xmlns=''http://www.w3.org/1999/xhtml''%26gt;
%26lt;head%26gt;
%26lt;meta http-equiv=''Content-Type'' content=''text/html; charset=utf-8'' /%26gt;
%26lt;title%26gt;Night Sky Media Designs Graphic Design%26lt;/title%26gt;
%26lt;style type=''text/css''%26gt;
%26lt;!--
body {
background-image: url(Images/starbacker-greyscale.jpg);
}
.style1 {color: #FFFFFF}
.style2 {color: #FFFFFF; font-weight: bold; }
--%26gt;
%26lt;/style%26gt;
%26lt;script src=''../Scripts/AC_RunActiveContent.js'' type=''text/javascript''%26gt;%26lt;/script%26gt;
%26lt;script type=''text/javascript''%26gt;
%26lt;!--
function MM_preloadImages() { //v3.0
?var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
?var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i%26lt;a.length; i++)
?if (a[i].indexOf(''#'')!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}