Gmail Interface – Weird Close Button on Right Bottom Corner Explained

If you're using Chrome, the wasted empty space can be removed by install the Chrome extension Webmail Ad Blocker.

Once installed, go to the Manage Extensions page in Chrome and choose Options for this extension. Then under the Gmail tab, on the right, turn off the tick labelled "People Widget". Note: this is better than turning it off in Gmail settings because the wasted space is also removed.

While I also have AdBlock Plus installed, I have found adding this extension along side it to be a better solution than adding a mail.google.com##TD.Bu:last-child filter to AdBlock Plus because that filter also causes emails to be completely blanked out when the email page is displayed by clicking a desktop notification for a new email received.

This was given by an anonymous user

I tried all the suggestions you had, then just today I found the following link in a thread where people were having the same problem with a blackberry. If you login to the gmail account and then go to the following url it seems to reset app. Hopefully it will work for you too. https://mail.google.com/mail/h/

Here is the link to the thread where they found it. http://supportforums.blackberry.com/t5/BlackBerry-PlayBook/No-Gmail-Help/m-p/1205879#M11063