I would guess it depends on the content and design of the site. Out of interest, tell us more about the project/site. Another thing, I have personally found text to be harder to read on tv monitors than computers but I have not experimented much with it.
Give us more info and let us know how it goes.
We are going to display a web-page that is going to show up on the widescreen TV monitors in the school I work for. It's going to be an html page that will have a header, body and footer in it. There will be a flash banner and a place for a video to show up as well as text information.
I know it would be great to do this as a fullscale flash page, but the want t his updated dynamically so I am leaving it up to the back-end programmers to take care of this.
I guess the key fact is it will be displayed on Widescreen televisions. The webpages will display the videos our students upload.
I have not worked in percentages in Dreamweaver, but I can't help if this is what I should do.
I would go for percentages because they could probably adapt better to fit a widescreen tv. It depends on the tv also and how it scales whatever input you use to display the webpages. If it is videos then it will not be so much an issue, but if you there is a lot of text then it would be more complicaed because it might be harder to read on a tv if scaled. But I am no expert in this. I guess you need to look at the technical setup you are using.
Best thing you can do is build a quick prototype/beta site and then test it on the tv with some quick video uploads etc. A quick test is porbably the best way to get your anwser. And you may also find new things you have not considered. Also keep testing it on the tv as you further develop it.
I would suggest going with clear, rather wide fonts specifically developed for the Web such as Georgia, Verdana, Constantia, etc. Cyjetsu is right, text does generally display less well on tv monitors than on computer displays. Using fonts such as Times New Roman, Tahoma, or Arial will decrease readability. And make sure the specific fonts are installed on the school computers, or you'll get Arial or Times NR every time.
(If you're using a Mac system, try Charcoal, Palatino, or Garamond on the displays, though you may have some of the Windows fonts listed above. Since you're coding for a school, I doubt very, very seriously the school is Linux-driven.)