If you installed SPIP in its 2.1 version, a bug  introduced 10 months ago  made all your articles “disappear” on your website. No panic, only their display is being broken, a simple upgrade to SPIP 2.1.2 will solve the issue.
The bug appears in the file
In this file, at the line 82, you just need to replace the value
: (time()+(3600*24*10000))) ;
: (time()+(3600*24*365*2))) ;
All usual upgrade methods are possible:
— editing the file
ecrire/public/quete.php on your site (cf. former code)
spip_loader.php to download and install SPIP 2.1.2
— downloading SPIP 2.1.2 and upgrade the whole site by FTP.
— downloading the patch: http://trac.rezo.net/trac/spip/changeset/16014
— pulling from SVN by
svn up ecrire/public/quete.php if your website is on SVN with 2.1 branch
— using the unix command: This command, executed as root, allows you to fix the problem globally for all instances of SPIP on your server:
(This command displays files fixed).
Then EMPTY THE CACHE of your website, and you’ll be good to go again.
With our deepest apologies for this (great) mistake!