When using SharePoint Designer 2010 to connect to a SharePoint and SharePoint online website, the application prompts the user to login for the first time. After the user has logged on once, the application caches this information and automatically logins to the website the next time you try to open the website. This is a desirable feature, but there is often the case when we want to login as a different user, and SharePoint Designer continues to auto login with the credentials already cached.
To be able to login as a different user, one needs to first let the application automatically login to the website. Once the website is open on the designer, there is a face icon on the bottom-left of the application as shown below:
|Click to change user|
If you click on the icon, the application displays a dialog indicating that you are logged on as a particular user and if you want to login as someone else. Click ok, and enter the new credentials. This should allow you to login as a different user, and you can go on with your tasks.