You're welcome, John.
If you take a look at the
XHTML Validator there are a few, easily fixed HTML issues.
Most of the cited errata are due to a couple of lines in your flyout-menu.xml
<item caption="Jetstream" link="https://www.ventusky.com/?p=25.0;-53.8;3&l=wind-300hpa" target="_blank"/>
and
<item caption="Historical Data" link="http://www.findu.com/cgi-bin/wxpage.cgi?call=FW0917!Westminster&last=120" target="_blank"/>
<item caption="Data Quality" link="wxcwopstats.php"/>
<item caption="NWS CWOP Data Feed" link="https://www.wrh.noaa.gov/mesowest/timeseries.php?wfo=mtr&sid=F0917&num=48" target="_blank"/>
<item caption="MesoWest Data Feed" link="https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=F0917" target="_blank"/>
in each of the link= strings that contain '&', you need to replace those with '&amp;' to make the XML validate.
Example
<item caption="NWS CWOP Data Feed" link="https://www.wrh.noaa.gov/mesowest/timeseries.php?wfo=mtr&sid=F0917&num=48" target="_blank"/>
would become
<item caption="NWS CWOP Data Feed" link="https://www.wrh.noaa.gov/mesowest/timeseries.php?wfo=mtr&amp;sid=F0917&amp;num=48" target="_blank"/>
This funny stuff is caused by the XHTML requirement that ampersands can't be 'naked' and have to be done as HTML entities & - The XML parser will automatically change & to & itself, so the &amp; gets changed to & which leaves the proper HTML entitity in place for the URL in the HTML, and the browser itself will replace the remaining & with & when the URL is clicked.
Doing these changes in your flyout-menu.xml will remove a bunch of XHTML errata from the validator.
You have a line
<link href="css/hover-tiny.css" rel="stylesheet" media="all"
which is both incomplete and in the <body> section of the page. Change it to
<link href="css/hover-tiny.css" rel="stylesheet" media="all" />
[/code] and move it to above the </head> line in the page. Then revalidate to see if the errata are now gone.