I know this is something I'm probably doing wrong, so please don't incinerate me for the thread title.

I'm trying to put together a small personal website using HTML 5/CSS3. I've checked with the w3c validator and the site and CSS file fully conform according to the validator (However the validator has a warning attached that it might not be perfect).

I'm not sure how to explain it without a picture, so here's a comparison of Chrome/Opera/Firefox:

So, you can sorta see how in Chrome the background image is in one non-repeating piece, whereas in Opera/Firefox the image has, oddly, been broken up and placed slightly differently.

I'm confident this is due to an error on my part, but I've had no luck at all figuring out why the image is being mangled in Opera and Firefox.

Here's the CSS that's relevant to this issue:

/* Content Pane */         
.content
{           position: absolute;
            left: 220px;
            width: 800px;
            top: 80px;
            min-height: 550px;
            background-color: rgba(8,12,42,0.85);
}

/* Headers */
.content hgroup 
{
            background: url("Header_Flat.png") no-repeat left top;
            min-height: 38px;
            padding-left: 28px;
            text-shadow: 0 0 8px #FFA9FF;
            color: Black;   
            text-decoration: none;  
}

.content hgroup h1 
{
            display: block;
}

.content hgroup h3
{
            display: inline;
            position: relative;
            top: -12px;
            left: 20px;
            text-shadow: 0 0 6px #AFF9FF;
}

.content hgroup h4
{
            display: inline;
            position: relative;
            top: -12px;
            left: 20px;
            font-size: xx-small;    
            text-shadow: 0 0 6px #AFF9FF;
}

And the HTML:

<hgroup> 
    <h1>New Site!</h1> 
    <h3>Now with Bloom!</h3> 
    <h4> - Posted Tuesday, May 11th 2010</h4> 
</hgroup>

Can anyone see what I'm doing wrong?