word replace

how do you tell a page to replace a certin word with another specified word everywhere its listed on the page. I don't mean like find and replace I mean like at run time.

Quick & dirty way

function replaceWord( word, replacment )
{
var pattern = new RegExp( word, "i" );
document.body.innerHTML = document.body.innerHTML.replace( pattern, replacement );
}

Best off doing this server-side before the page is returned to the client in many cases - but of course, that depends on your purpose. Which is?