When you customize Microsoft Dynamics CRM 2013 and Microsoft Dynamics CRM Online you will typically work within the solution explorer for the default solution. To open the default solution navigate to Settings > Customizations and select Customize the System. The solution explorer for the default solution will open in a new window or tab depending on how your browser options are set.
After the Solution explorer opens, use Ctrl+D to create a favorite or bookmark in your browser. This will help you open it faster even if you don’t already have the web application open.