Creating resizable website with lack of CSS skills - CSS shapes

Question

This is my first question here, so please point out any of mistakes that I made.

I was obliged to create a web page that looks like a flag of a team. I've managed to do such, but only with fixed size of elements :

On other resolutions it just doesn't fit the screen.
Code:

html

<div id="centered">
    <div id="triangle-down"></div>
    <div id="triangle-right"></div>
    <div id="triangle-left"></div>
    <div id="triangle-up"></div>
    <div id="diamond-narrow"></div>
</div>

css

    #centered {
        position:relative; clear:left;
        height:766px; width:1245;
        margin:0 auto;
        background:#fff;
        z-index: 0;
    }

    #triangle-up {
        position: absolute;
        margin-left: 281px;
        margin-top: 555px;
        width: 0;
        height: 0;
        border-left: 341px solid transparent;
        border-right: 341px solid transparent;
        border-bottom: 211px solid #3b5998;
        z-index: 1;
    }

    #triangle-down {
        position: absolute;
        margin-left: 281px;
        width: 0;
        height: 0;
        border-left: 341px solid transparent;
        border-right: 341px solid transparent;
        border-top: 211px solid #3b5998;
        z-index: 1;
    }

    #triangle-left {
        position: absolute;
        margin-left: 902px;
        margin-top: 171px;
        width: 0;
        height: 0;
        border-top: 211px solid transparent;
        border-right: 343px solid #3b5998;
        border-bottom: 211px solid transparent;
        z-index: 1;
    }

    #triangle-right {
        position: absolute;
        margin-top: 171px;
        width: 0;
        height: 0;
        border-top: 211px solid transparent;
        border-left: 343px solid #3b5998;
        border-bottom: 211px solid transparent;
        z-index: 1;
    }

    #diamond-narrow {
        margin-left: 342px;
        width: 0;
        height: 0;
        border: 280px solid transparent;
        border-bottom: 173px solid red;
        position: absolute;
        top: -70px;
}

    #diamond-narrow:after {
        content: '';
        position: absolute;
        left: -280px; top: 173px;
        width: 0;
        height: 0;
        border: 280px solid transparent;
        border-top: 173px solid red;
    }

Here's a jsfiddle of my flag: click
As you can see I am using css shapes to draw triangles and a diamond. My questions are:
How can I make that flag (web page) to fit different screen resolutions? How to present width and height of my shapes in percentages?
As I have read here, eg. border-left can not have a value in %.

EDIT
Thanks to @joe_coolish, I managed to make that web page resizable. However, I got one more problem.
Here's my html:

<table width="100%" style="height: 100%;">
    <tr>
        <td width="10%" height="10%"></td>
        <td></td>
        <td width="10%" height="10%"></td>
    </tr>
    <tr>
        <td width="10%" height="10%"></td>
        <td id="centered" bgcolor="white">
            <div id="main"/>
        </td>
        <td width="10%" height="10%"></td>
    </tr>
    <tr>
        <td width="10%" height="10%"></td>
        <td></td>
        <td width="10%" height="10%"></td>
    </tr>
</table>

Changes to Joe's code:

var main = $('#main');

function update() {

var height = $('#centered').height();
var width = $('#centered').width();

...

$('#centered').resize(function () {
update();
});

Now when I load my page, this happens:
I have to inspect some element to work it properly. Why?

Answer 1

You could also go with SVG.

More math, but it does work pretty well. Just attach to the $(window).resize() event and then update the triangles. Here is my first attempt:

var main = $('#main');

function update() {

    var height = $(window).height();
    var width = $(window).width();

    var height10 = height / 5
    var heightMinus10 = height - height10;
    var width10 = width / 5
    var widthMinus10 = width - width10;

    var height2 = height / 2;
    var width2 = width / 2;
    var width3 = width2 - width10;
    var height3 = height2 - height10;
    var width3x2 = width2 + width10;
    var height3x2 = height2 + height10;

    var points1 = '0,' + height10 + ' 0,' + heightMinus10 + ' ' + width3 + ',' + height2;
    var points2 = width10 + ',0 ' + widthMinus10 + ',0 ' + width2 + ',' + height3;
    var points3 = width + ',' + height10 + ' '+width+',' + heightMinus10 + ' ' + width3x2 + ',' + height2;
    var points4 = width10 + ','+height + ' ' + widthMinus10 + ','+height+' ' + width2 + ',' + height3x2;
    var points5 = width3 + ',' + height2 + ' '+width2+',' + height3 + ' ' + width3x2 + ',' + height2 + ' ' + width2 + ',' + height3x2;

    var svg1 = '<svg height="' + height + '" width="' + width + '">'+
        '<polygon points="' + points1 + '" style="fill:blue" />'+
        '<polygon points="' + points2 + '" style="fill:blue" />'+
        '<polygon points="' + points3 + '" style="fill:blue" />'+
        '<polygon points="' + points4 + '" style="fill:blue" />'+
        '<polygon points="' + points5 + '" style="fill:red" />'+
        '</svg>';

    main.empty();
    main.append($(svg1));
}

update();

$(window).resize(function () {
    update();
});

http://jsfiddle.net/ePt62/