you can access your plugins via FTP
FTP is connected to your web hosting account
the login credentials are available from Yahoo since they are your webhost
after you can get into your files via FTP
find the WP Content folder
within that folder is the PLUGINS folder
you can delete problem plugins from that folder without having access to your WordPress Admin Dashboard.
if a plugin is the source of the problem causing the white screen, then removing the plugin is the solution that i have found works to fix.