Webdesign: CSS and FF issue

     Hi! I'm new to webdesign and currently making a website. I'm
having some problems with css, that i'm only using to format the text.
In IE everything looks fine, but in FF paragraphs are getting
overlapped, and it really looks messy! In IE i managed to make the
site look fine only by deleting the first lines of the HTLM code that
refer to Doctype.
     I'm really stuck and i could use some help! Can someone help me?
Thanks on advance!

Here goes the Css code:

p{
        font-family: Verdana, Arial, Helvetica, sans-serif;
        font-size: 16px;
        font-style: normal;
        line-height: 1.5;
        color: #000033;
        text-indent: 40px;
        height: 10px;
        text-align: justify;
}

.titulo{
        font-family: Verdana, Arial, Helvetica, sans-serif;
        font-size: 20px;
        font-style: normal;
        line-height: 1.5;
        color: #000033;
        text-indent: 50px;
        height: 15px;
        font-weight: bolder;
}

.sublinhado{
        font-family: Verdana, Arial, Helvetica, sans-serif;
        font-size: 16px;
        font-style: normal;
        line-height: 1.5;
        color: #000033;
        text-indent: 40px;
        height: 10px;
        text-decoration: underline;
}

.titulo1{
        font-family: Verdana, Arial, Helvetica, sans-serif;
        font-size: 18px;
        font-style: normal;
        line-height: 1.5;
        color: #000033;
        text-indent: 50px;
        height: 15px;
        font-weight: bolder;
}

.lista{
        font-family: Verdana, Arial, Helvetica, sans-serif;
        font-size: 16px;
        font-style: normal;
        line-height: 1.5;
        color: #000033;
        text-indent: 40px;
        height: 10px;
        list-style-type: circle ;

}

html, body {
margin: 0;
padding: 0;
}