That's the desktop background. Depending on your OS right click a blank space on the desktop (ie. no icons) and select 'personalise' - try to change settings. See if they 'stick' for want of a better word. Reboot and change settings back to original. See if that helps.
What is Markdown?
Markdown lets you add more formatting to your post. Simply type in your post and it will display as written.
If you wish to add bold or italic characters, add a hyperlink to another website, a heading or a horizontal line, simply use the relevent icons above the text input field.
A preview of your post will appear in the grey box below. If you make a change and you're not happy, simply press the back arrow icon to undo.