javascript popup problem

I am trying to print a asp.net gridview by using javascript,i've put the entire gridview inside a div element and send it to javascript file,it is working perfectly,the only problem I have is to remove the STYLE that I have in ASP page and instead add a new style in javascript file,I have this piece of code:

could anybody help me out with this problem?

var oldHTML = document.getElementById(print_area).innerHTML;
var newHTML = "<div style='background-color:Blue'>" + oldHTML + "</div>";
document.getElementById(print_area).innerHTML = newHTML;
pp.document.writeln(newHTML);