firefox 3.6.19 rendering bug - html

Question

In my project i have master page that looks like this:
<asp:Content runat="server" ID="content1" ContentPlaceHolderID="Content">
<div id="RightBar">
<asp:PlaceHolder runat="server" ID="plhRightbar"></asp:PlaceHolder>
</div>
<div id="content">
<asp:ContentPlaceHolder ID="MainContent" runat="server"></asp:ContentPlaceHolder>
</div>
</asp:Content>
for some reason ff 3.6 renders the <div id="content"> inside <div id="RightBar">, needless to say that this behavior is messing with the whole website layout.
this bug is happening only in ff 3.6, even IE6 render it correctly.
so far i tried the following steps:
1. changing the DOCOTYPE.
2. looking for unclosed tags inside each placeholder.
3. changing css.
the css:
#RightBar{float:right;width:225px}
#content{width:707px;float:left;overflow:hidden}
but none of these work.
any ideas?
EDIT: i can't give you a link because it still in development, but in ff 3.6 it looks like this:
<div id="RightBar">
...right bar content here...
<div id="content">
...content here...
</div>
</div>

Answer 1

My first impulse is to get rid of the float:left; for content or at least change it to float: right; (several floats on the same side stack upon each other when there is enough room)
If that fails, try using a table to get the layout you want. Yes, I can hear you cry out in horror but the rule for tables is "use tables only when they make sense" and not "never ever under no circumstances whatsoever use tables".

Answer 2

I suggest running the generated HTML code through the W3C Validator -- it sounds very much as if you have some kind of HTML syntax error; I can't see it in the code you've posted, but the validator will pick it up.
Use the browser's 'view page source' option, and paste the whole thing into the validator's text area.
The validator can be found here: http://validator.w3.org/