// ==UserScript==
// @id             usur scrupt
// @name           usur scrupt
// @namespace      somtammytam
// @description    replaces vowels with u's
// @include        *
// ==/UserScript==

String.prototype.uize = function() {
  return this.replace( /([AEIOUaeiou])/g, function(m,p1,p2){ return "u";} );
};

var xPathResult = document.evaluate(
'.//text()[normalize-space(.) != ""]',
document.body,
null,
XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
null
);
for (var i = 0, l = xPathResult.snapshotLength; i < l; i++) {
var textNode = xPathResult.snapshotItem(i);
textNode.data = textNode.data.uize();
}