I did not get the active content warning from TheaterView but it could not load the page until I changed the security settings to "allow active content in local files" as AnalogRoaming suggested.
I think the presentation is very nice. I use 800x600 for tv out so I had to remove some things and change font sizes for it to fit on 1 page but this was very easy the way you have it set up with a style sheet, etc. On a side note, it would nice if they would allow us to give the "browser window" the focus with a right-arrow so that I could scroll vertically with my remote. The only look I changed was the extended forecast text from yellow to white because it was a little hard to see on the gray-ish table background on my display.
I have run into some strange behavior in Internet Explorer. Every once in a while when I open the weather page in TheaterView, one of the "cells" in the extended forecast table is taller than the rest of them. It seems totally random and if I go back and reopen it right away, the problem goes away (they are all vertically the same size). Weird...