We had an outage on our PLoS.org domain resources yesterday due to a DNS issue. As a result, www.plos.org and all of the plos.org subdomains were intermittent as well. The issue was addressed promptly but there was a 2-10 hour delay while DNS servers were updated and ~24 hour delay before a comprehensive international DNS update. Most people were able to access www.plos.org within a few hours.
The DNS issue did not affect any of the PLoS journal websites.
Please be aware that if doi.plos.org is down, you can use CrossRef for DOI resolution.