When I tried to edit the home page of my application, I came across the error "The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again". This issue is caused because of security validation.
You can follow the steps to get rid of the error -
1> Go to Central Administration --> Application Management
2> Click on Web Application General Settings
3> Go to Web page Security Validation and select the Off radio button. Then click on OK.
4> Refresh the page and Iwas able to edit the page.
Hope this helps someone.