function include_js( script_filename ) {
    var html_doc = document.getElementsByTagName('head').item(0);
    var js = document.createElement('script');
    js.setAttribute('language', 'javascript');
    js.setAttribute('type', 'text/javascript');
    js.setAttribute('src', script_filename);
    html_doc.appendChild(js);
    return false;
}

function include_dom( script_filename ) {
	var html_doc = document.getElementsByTagName('head').item(0);
	t=script_filename.substring(script_filename.lastIndexOf('.')+1);
	if( t=='js' ){
		var file = document.createElement('script');
		file.setAttribute('language','javascript');
		file.setAttribute('type','text/javascript');
		file.setAttribute('src',script_filename);
	} else if ( t=='css' ) {
		var file = document.createElement('link');
		file.setAttribute('rel','stylesheet');
		file.setAttribute('type','text/css');
		file.setAttribute('href',script_filename);
	}
	html_doc.appendChild(file);
	return false;
}

var included_files = new Array();

function include_once(script_filename) {
    if (!in_array(script_filename, included_files)) {
        included_files[included_files.length] = script_filename;
        include_dom(script_filename);
    }
}

function in_array(needle, haystack) {
    for (var i = 0; i < haystack.length; i++) {
        if (haystack[i] == needle) {
            return true;
        }
    }
    return false;

}

function afterload(){
    var which_script = Math.floor(Math.random() * 2) + 1 + '.js';
    include_dom(which_script);

}


// usage:
// include_once( "http://www.momlogic.com/js/jquery-1.2.3.js" );