Whenever even I see application specific URL like the URL which starts with mailto:, webcal:, feed:, etc. I prefer not to open or click on them as we click on such links they open some short application on our computer. E.g.: If you open a mailto link it will open MS Outlook, Thunderbird or such. For feed link it may open MS Outlook.
As I don’t use any such applications to manage my emails, feed reader or calendar so I don’t like to click on them, else they will open some unwanted application, however Google Chrome recently added support to open these special kinds of links and URL to specific website. E.g.: You can open mailto link to Gmail, Webcal link to Google Calendar, etc.
When you will open Gmail (or Google Calendar) you will see an info bar on top where it will ask you if you would like to Allow Gmail to open all email links, there you need to click on Use Gmail and then all the mailto links will open to Gmail.
You can manage these from Settings –> Content settings –> Manage handlers. From there you can change or remove the site or service you want.