Occasionally a site user or developer will navigate to a page and suddenly the page content disappears, and is completely blank. No content. No errors. Nothing. This often, but not always, happens after updating a module, theme, or Drupal core. This is what is referred to by most members of the Drupal community as the White Screen of Death or WSOD. There are several reasons why this might occur, and therefore several possible solutions to the issue.
For how to solve this problem, look here.