GPXviewer do not start local with any browser. Please copy to the web.
You have to integrate it as any other flashfile.

<object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000"
codebase="http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0"
width="600" height="400" id="gpxviewer" align="middle">
	<param name="swLiveConnect" value="true">
	<param name="allowScriptAccess" value="sameDomain" />
	<param name="movie"
           value="gpxviewer.swf?gpx=http://www.yourDOMAIN.com/yourSUBDIR/yourGPX.gpx&zoom=14" /> 
	<param name="quality" value="high" />
	<param name="scale" value="noscale" />
	<param name="salign" value="lt" />
	<param name="bgcolor" value="#ffffff" />
	       <embed src="gpxviewer.swf?gpx=http://www.yourDOMAIN.com/yourSUBDIR/yourGPX.gpx&zoom=14"
	                  quality="high"
	                  scale="noscale" 
	                  salign="lt" 
	                  bgcolor="#ffffff" 
	                  width="600" 
	                  height="400" 
	                  name="gpxviewer" 
	                  align="middle" 
	                  allowScriptAccess="sameDomain" 
	                  type="application/x-shockwave-flash" 
	                  swliveconnect="true" 
	                  pluginspage="http://www.macromedia.com/go/getflashplayer" />
</object>

Note up: Your .gpx. file is included at this point:

<param name="movie" value="gpxviewer.swf?....... and 
<embed src="gpxviewer.swf?......

The first and the last point are marked as a green and a red point.
If your .gpxfiles are on another domain write a file like this:

<?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
        <allow-access-from domain="*"/>
</cross-domain-policy>

You have to call the file crossdomain.xml and save it on the web-root-directory of the targetdomain. Flashfiles will check this file for secrurity.

You can't change the size of the viewer on this version.
You need no registration for this viewer, but it is necessary to register at http://www.google.com/apis/maps/signup.html
Include the registration on your website.

<script src="http://maps.google.com/maps?file=api&v=2&key=ABQIAAAABWmbKe......mYqu55sfdg" type="text/javascript"></scrip>

We explicitly point out that we do not take any responsibility, neither for the usage of the viewer, nor for the displayed routes.

We hope you enjoy the GPXviewer.