Whether you have a hugely popular blog or getting just a few visitors per day, you still want to make sure that your site is up and running all the time. And that no hackers have sprayed graffiti on your blog with the intention of defacing your website. In either of these emergency situations, you want to be notified immediately over email or an SMS on your mobile phone and Site24x7 will help you with just that and more for free. It is from the same company, AdventNet, that develops the powerful Zoho Web Office Suite.
You can think of Site24x7 as your personal site monitoring assistant that continously monitors websites for you and immediately issue an alert when there's some unusual change on the design or when the blog site is inaccessible [offline] or when some webpage is returning a "page not found" error or taking too long to respond.
Here's a typical configuration dialog to monitor your site or a URL. You can put your blog title or description in the keyword area so if anybody hacks the site replacing these titles with his own messages, you are informed that very instant.
The service tracks data for the last 30 days with an history long and chart for the server response time. This details can also help when you need to get hold of your ISP's neck.
The developers AdventNet even provide a free desktop version of the URL monitoring software that does a few things more like retrieving the entire content of the webpage.
Site24x7 - Website Monitoring Service [Thanks, ResourceShelf]