CSS - Internal Or External Css?

Hey, I'm a CSS noob, and I'm having some trouble with centering the content of my page. When I have the coding as an internal style sheet the page is centered, but when I put it in an external style sheet it looks the exact same...except for that it's left aligned. All I do is copy and paste it, but it change the layout around? Any tips?

Is there a way to only clear floats within an element without affecting any floats defined about and outside the element?

example:

<div style="float:left;">A</div>
<div style="float:right;">
<div style="float:left;">C</div>
<div style="clear:both;"></div>
</div>

I would want the clear to only clear C and not A

so...
having this problem where i have some css styles applied to form inut boxes, and one of them asks for the user to input his/her email address. IE, thinking it's being helpful, is overriding my nice green background with an ugly yellow background.

I've done some testing, and if i put the word "email", "e_mail", "e-mail", or even "mail_e" in either the html text NEXT to the blank, or in the name of the INPUT tag, IE assumes i want it to be yellow.

any way of overriding this?

CSS:
Code:

.inputBox {
	border: 1 solid black;
	background-color: #bcdd4a;
	font-size: 12;
	width: 200;
	height: 16;
	color: #145e16;
	font-weight: bold;
}

HTML:
Code:

<td valign=top>E-mail:</td>
<td valign=top><input type="text" class="inputBox" name="emailAddress" size=20></td>

IE Version: 6.0.2800.1106
LINK: http://www.t-2.biz/contact.php

please help, frustration setting in.

cheers \\ kfancy

Im kinda new in CSS so sorry if this is a noob question
Im having trouble making an external stylesheet because for some reason my html is just not loading the .css file. But I also read that an external is a little slower aswel if i'm not mistaken, because it has to read another file.
But I'm in the internal stylesheet is working good but I noticed I can't create a new class using the "." before the word. Is there anyway I can create a class using the css inside the html file?

Here's the template I'm working on: http://dhost.info/justusvizslas/template.php

Here's my problem:
I'm trying to create a centered, two-column layout with a header and a footer, sort of like the tutorial he http://nemesis1.f2o.org/aarchive?id=7

I've got everything working correctly and it looks fine in IE. However, in FireFox, the container div doesn't automatically adjust its height to be the same as the height of the divs inside. Instead, I have to set the height at a certain number of pixils to even get the container div to show up. When I do that, in IE the container div defaults to the same height as the larger of the two inner divs, but in FireFox the container div just stays at whatever pixil height I specified. That becomes problematic because I don't plan on having all my pagecontent divs with the same height.

Any insight will be greatly appreciated. I've been looking at this for hours and haven't gotten it to work like it should. Here's the relevant code too:
CSS
Code:

#container {
		width:792px;
		height:50px;
		margin: auto auto;
		color:#000000;
		background-color:#FFFFFF;
		background-image:url(design/menuimage.gif);
		background-repeat:repeat-y;
		}
		
#navigation {
		width:125px;
		height:auto;
		padding:0px;
		float:left;
		margin-top:auto;
		vertical-align:top
		}

#pagecontent {
		width:667px;
		height:auto;
		padding:0px;
		float:left;
		margin-top:auto;
		color:#000000;
		background-color:#FFFFFF;
		text-align:center
		}

PHP
Code:

<div id="container">
  	<div id="navigation"><?php include "nav.php"; ?></div>  
	<div id="pagecontent">
  		<br />Some more content here<br />
	</div>
</div>

Again, thank you in advance for any help with this. If you're stumped and think it should work as-is, go ahead and go to the actual template I'm working on (first http link in this post) and look at it in IE and in FireFox to note the difference.