I added K2 User module in my website, but when I click on add item from the home page, the k2 new item appear but all the tabs are opened, like there is an error in the page while loading

Hi. Check your page for javascript errors.

what exactly I should do ?

Probably there is a javascript error on your page. The error may coming from anywhere, extensions or template. Try to check your jQuery handling settings under K2 parameters. Finally if that doesn't help post a link to your site.

this is my site:

www.manchette-mag.com

thank you :)