There are few occasions when you face the problem of blank page or blank screen problem in the WordPress. These type of problems persists mostly when a new plugin or a new wordpress theme is installed on you web hosting account. Though these errors can be fixed but when they occurs, its very frustrating time for webmasters because he becomes unable to see log in screen and faces a blank white screen. The main cause behind these type errors are incompatibility of that particular plugin or theme with your wordpress version due to certain error in the the PHP code.
The first step to be taken while handling such errors is to deactivate all your plugins and recheck the website. If the website appears up then there problem is surely with the plugins. After this you need to activate the plug in one by one and check the website after activation of each plugin, by adopting this method you can sort out the problematic plugin causing for the error. Once this plugin with problem with it is identified you should search for another substitute plugin which can be used as a replacement of it and also is compatible with your wordpress version.
But the basic question you may have now that ‘how to deactivate or activate the plugins as you are not able to login in to the wordpress dashboard?’ For that you can refer this http://www.host.co.in/knowledgebase/how-to-deactivate-activate-plugins-or-theme-without-logging-into-wordpress-dashboard