This post gives you the information on how to clear the cache which is created by SharePoint Designer. Generally when you log in to the designer you see the info of already opened sites/pages . This is due to the cache which is created by designer when you login/open the site.
Follow these steps to clear the cache.
Close the designer and delete the files from below folders(Open these folders in windows explorer)
- %APPDATA%\Microsoft\Web Server Extensions\Cache
If you want to clear the cache frequently ,write a batch file with these commands to run with single click.