First of all, the parameter list shouldn't have "var" in it, so it should look like this:
Code:
function tR(str1, str2){
Second, the function call can't be in the same SCRIPT element that refers to src.js, since it would be ignored then.
In order to make the HTML valid there should also be a type="text/javascript" attribute in the SCRIPT start tags, and it's probably more correct to use DOM manipulation instead of document.write, but the above two changes seem sufficient to make it show up in Firefox and Opera, at least.