VB CSS Trouble Div autosize

Hello trying to get my website to display correctly having trouble. I am using CSS and it looks completely different in firefox compared to IE however neither do what i need it to do.

I have vb validators that when something is not inputed in the the textboxes it displays label messages that you need to input something. But my main div is not expanding when they click the submit button and the labels appear they just appear under the footer and out the bottom of the webpage.

body  
{
    /*font: 100%/1.4 Verdana, Arial, Helvetica, sans-serif;*/
    background: #42413C;
    margin: 0;
    padding: 0;
    color: #000;
    text-align: center;
    text-align: -moz-center;
}

#container
    {
        width: 1024px;
        background: #FFFFFF;
        margin: 0px auto 0px auto;

    }

#to开发者_开发问答pbanner
   {
       width: 100%;
       height: 75px;
       background: #ADB96E;
       color: #FFFFFF;
       text-align: center;
       font-size: 40px;
   }
    #maincontent
    {

        width: 780px;
        padding:5px 0;
        float:right;

    }

    #menunav
    {
        float:left;
        width:180px;
        background: #EADCAE;
        padding-bottom: 10px;


    }
    #footer
    {
        height: 50px;
        background-color: #ccc49f;
        position: relative;
        padding:10px 0;
        clear:both;

    }     

Thanks for the help

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Have you first included a CSS reset? You can find more information right here: http://meyerweb.com/eric/tools/css/reset/