The page has one or more asp:Content controls that do not correspond with asp:ContentPlaceHolder controls in the Master Page.

I kept getting this error in the design view:

The page has one or more <asp:Content> controls that do not correspond with <asp:ContentPlaceHolder> controls in the Master Page.

A few Google searches, this is what I found to work for me:

Setting
<title></title>
instead of
<title />
solved the problem.

http://forums.asp.net/t/1302708.aspx

Skype in the Windows 7 taskbar

Try searching Google to see how to get rid of the Skype icon off the taskbar.  There are mostly results that instruct changing the shortcut's Compatibility mode to SP2.  That sounds clever but Skype itself directly supports this.

Open Skype...
Click Tools in the menu bar...
Click the Options menu item...
a new window will open, click the Advanced button on the bottom left of the new window...

Skype should have a checkbox entry that says
"Keep Skype in the taskbar while I'm signed in."