You need a tag in the HTML code declaring the character set used,
otherwise LibreOffice seems to assume UTF-8. I don't know if Namo
WebEditor provides a dialog or other GUI to add the necessary tag, but
you need something like the following within the <head> section (ideally
near the top*):
<meta http-equiv="content-type" content="text/html; charset=Windows-1252">
If there's already a similar line, perhaps with the charset part missing
or incorrect, edit that line.
LibreOffice doesn't seem to recognise the HTML5 <meta charset="...">
style, so if you're currently saving the page as HTML5 it might be worth
trying HTML4 and Namo might add the appropriate tag for you.