Checking site uptime with Google Docs
There is no // try, catch, else in javascript. 

Instead I would do:

var success = false, state = null;
try {
    response = UrlFetchApp.fetch(url);                                        
    success = true;
    error = "Up";
    state = "Site up: ";
} catch(ex) {
    success = false;    
    error = ex;
    state = "Site down: ";
}

insertData(status, url, row, error, response.getResponseCode(), state);