The new 'eye' symbol is present in all the password fields in Internet Explorer 10 which comes default with Windows 8 (and is also available for Windows 7). To reveal the password, the user needs to keep the 'eye' symbol pressed.
Disabling it (in Windows 8):
Please note that to do the following, you will need to access the Local Group Policy Editor, which is only available in Windows 8 Pro. You can see if you have Windows 8 Pro by pressing Win+Pause, which opens the System Properties window. If under "Windows Edition" you see Windows 8 Pro, you will be able to access the Group Policy Editor.
To disable the "eye" symbol, follow these steps:
Open the Run dialog (Win+R)
gpedit.msc and press Enter
Local Group Policy editor will open:
Navigate to Computer Configuration → Administrative Templates → Windows Components → Credential User Interface:
Double-click on "Do not display the password reveal button" and select the "Enabled" option:
The behaviour is disabled, you can enable it with the same method.
Source: (From Wayback machine Web archive) Enable or Disable Password reveal option in Windows 8