Unable to access login page or my website
One small detail that can cause the front-end and back-end of your site to result in a blank white page, is if you have a syntax error in your general.php file, such as a missing comma at the end of a line.  If you've just made a recent edit to your config files, take a closer look at them and make sure that you don't have any small errors.

For example, the following multi-environment config is missing a comma at the end of the omitScriptNameInUrls setting, and that minor detail would make both the front-end and back-end of a site result in a blank white page: 

return array(
    '*' =&gt; array(
        'omitScriptNameInUrls' =&gt; true
        'devMode' =&gt; false
    )
);