If you did recently upgrade your WordPress blog to the latest version, there is a possibility your site turned totally white.

Don’t panic. One of WP your plugins must have been corrupted.
To easily fix this issue, I recommend you logging in to your website’s space, using FTP client, such as WinSCP. Once you are logged in, follow these steps:
1. Navigate to your home directory, usually named public_html.
2. Then go to: /public_html/wp-content and create a folder inactive-plugins.

3. Now go to the plugin directory and select all plugins and click right mouse button.
4. Select Move To…
5. Type the following directory: /public_html/wp-content/inactive-plugins/*.*. Usually you only need to change text from plugins to inactive-plugins and hit enter.

6. All your WordPress plugins are now deactivated and have been moved from /wp-content/plugins directory to /wp-content/inactive-plugins.
7. Voila, the white screen is now gone and you can now access your blog again!
8. Now restore all the plugins you have previously moved, back to their original /wp-content/plugins directory.
9. Start activating plugins from your wp-admin area; one by one to find out which plugin is giving you troubles. Make sure you perform this step carefully to prevent turning your site blank again.
10. When you find the buggy or conflicting plugin, just deactivate it again and wait until plugin’s author update his code.
Please note: In many cases you won’t find any conflicting plugin and your blog will run perfectly fine as before the upgrade. This particular problem can be also related to your current WordPress theme.
Extra 3 Tips: Do More to Secure & Maintenance Your Blog
1. Keep your plugins and WP release up to date.
2. Always create daily backups of your blog (database & file data). Or use a reliable plugin such as Hot Backup Manager to do this work for you.
3. Take website security seriously and act responsibly.

omg..i already thought i destroyed my site
thank you million times!!
Great. Removed SEO Ultimate from the plugin dir and site is back to normal. Bad thing is now I need a replacement, do you have any recommendations?
I am really glad it worked. I am sure you can find many decent alternatives in the official WordPress plugin directory.