JSTOR have been experiencing intermittent, site-wide access issues that affect use of JSTOR for the past couple of days. JSTOR engineers are working hard to restore stable access as quickly as possible.
Please check their 'Platform Updates' page (http://about.jstor.org/jstor-help-support/jstor-updates) for service alerts about these issues. They will post the most current information on that page, as it happens.
JSTOR apologise for this inconvenience