rocknbil - 4:41 pm on Aug 24, 2010 (gmt 0)

I was wondering if it is possible to use special CSS tags above h1 in order to use as a kind of Master Header.

I'm pretty sure this answers your original question, it's done quite often.

<h1>Page-Relevant Keywords Here</h1>

Say no to spam. Keep it relevant. :-) Then,

h1 {
display:block;
width: 800px;
height: 120px;
margin:0 auto 0 auto;
padding:0;
background:url(/path/to/uber-cool-header.jpg) top left no-repeat;
text-indent:-5000px;
}

Visually you are replacing the h1 itself with an image. The text indent renders the text invisible, but does not hide it. Semantically, you are keeping good document structure and relevance.