Fatal error: Call to undefined function cypher_previousposts() in wordpress

I have wordpress site. I have installed modern-blue-green-120070612-2 theme.Then i got an error message on the right hand side "Fatal error: C开发者_高级运维all to undefined function cypher_previousposts() in mydomain\wp-content\themes\modern-blue-green-120070612-2\sidebar.php on line 59.

Does any one know this? Please help me ....

Thaks in advance

cypher_previousposts seems to be coming from a plug-in named "Previous Posts" (see e.g. here). The author seems to be running the site cypherhackz.net. I'd recommend you search for this plugin in the official WP plugin repository and install it from there.