output to a specific location in html code

Hi. I have this issue:
I'm using a Java script (taken from a website) that detect screen resolution and apply a CSS for each size.
The code lucks like this:
if ((screen.width==1024) && (screen.height==768)) {
alert('Screen size: 1024x768');
$("link[rel=stylesheet]:not(:first)").attr({href : "CSS/grafica1024.css"});
}
In stead of alert message i what to publish in html code (in page position: down, i can use CSS for this(for positioning)) a text that say " Screen size : ...." or "Screen resolution: ..." (don't matter, is a fixed text).
I search on google and i found function document.write() but if i used my hole html page is rewrited. I dont want this, i want just to output a line in html with <p> in that code, not new page and if is posible to use CSS ( for positioning the text in page).
Thank u very much and sorry for my english