I want to use webpage monitoring tools which can keep track of changes to webpage. I want to monitor some webpages of websites for changes occurred in that pages and also changes in any files linked that page. In normal any webpages has some download links to text file,pdf file etc. So i want to keep track of changes to those files also including visible changes to the webpage.I searched a lot in Google and got some tools.They are convextra,changedetection.com. But all of them didn't work as i expected(eg.some don't compare changes in linked files) . So is there any good free web compare tool which can do it?