Question

I’ve been working on a footer for a blog. The footer generates a border around it, and I don’t know what has triggered it.

What could have triggered it?
Have a look at the website here: http://blog.sayhi.dk

 #footer {
    width:900px;
    margin-top:20px;
    margin-left:auto;
    margin-right:auto;
    height:200px;
}

  #footerstyle {
    background-image: url(images/bbg.png);
    width: 100%;
    clear:both;
    margin-top:20px;
    height:200px;
}

Answer 1

Your body has a margin.

body {
    margin: 0;
}

I’d recommend to use a CSS reset file like YUI Reset to remove such oddities and inconsistencies between different browsers.