html, information window

HTML works fine in my tests. It looks like in your case it’s being escaped before it is passed to BGMP, either because it wasn’t entered correctly in the editor, or by another plugin/theme.

Try editing the placemark and clicking the Preview button to load it directly, then check if the HTML is correct there. If it’s not, fix it in the editor.

If it is, try temporarily disabling all your other plugins and switching to the TwentyTwelve theme and check if it works. If it does, re-enable your plugins one-by-one until you find the one causing the problem.