neijunior,
Sorry that you are seeing this issue. Thank you for the details and the screenshot.
Can you please let us know how exactly you have installed Darkest Dark plugin to Eclipse?
The url mentioned in the error dialog : http://marketplace.eclipse.org/marketplace-client-intro?mpc_install=3274405 is not the update site for Webclipse
Please check if the above mentioned url is added to the Available Software Sites at : Window > Preferences > Install/Update > Available Software Sites. If yes, then select the entry and click ‘Remove’.
The correct update site for Webclipse is : https://www.genuitec.com/updates/webclipse/ci/
Ensure that it is listed in the Available Software Sites page and then try ‘Check for Updates’.
Please let us know how it works for you.
–Swapna
MyEclipse Support