Since Skype 5.10 and above the web-based Skype login/sign-in in window has been around. This window requires a functioning IE (for .html), javascript (.js) and cascading style sheets (.css). Any break in any of those will cause the window not to be displayed correctly.
The HKEY_ROOT value for .css is a global setting that tells the operating system how to treat .css files. CSS is a style sheet language that generally provides additional formatting for .html (Hyper Text Markup Language). Both .html and .css files are treated by the operating system as text (by default). In contrast, Javascript is a programming language and is treated like an application.
If .css files are set to execute as an application, it will not execute at all and all page formatting will be lost. In most cases you can still login to Skype if you type in your account info, but it will not look pretty.
There is probably a 3rd party program that toggled this setting, possibly a web editor so it could act as a middleman to those files. I would recommend changing it back to the default. If you find you have a program that requires it to be reversed, you can always change it back.
In the attached css.zip files you will find:
fix_css.reg - sets to text (fixes login window formatting by setting it to text)
break_css.reg - sets (breaks login window formatting by setting it to application)
Exit completely out of Skype then double click on the fix_css.reg. If this assignment was the only
thing breaking css, then it should fix the login window. To revert at any time, click on the break_css.reg file
There were design changes in the cached web data that houses the .html, .css, and .js files (%programdata%\apps) in 6.10. I tend to recommend people delete the Apps/login folder, then re-install the latest Skype to ensure the contents of %programdata%\apps are refreshed due to the major changes in that cached content. Just as bad as having the improper .css assignment is not having the correct .css and other related files on the hard drive.
Download
source : http://community.skype.com/t5/Windows-desktop-client/Skype-6-10-0-104-BIG-Login-screen-problem/m-p/2104915/highlight/true#M202212
