Simone, please provide screenshot and the exact steps how to reproduce that. Also, can you please try to reproduce this on our demo. 

Hi ross,

i've found the error...it's my custom theme.

What row of css code must I add to my theme tho have last mobile theme?

Thank you

I'm sorry I can't provide you such instructions as we do not provide assistance with 3rd party themes or plugins or customized default items. 

The latest mobile theme is available if the theme is compatible with the latest version of the software. 

And mobile forum is the part of the forum plugin. So it is a theme issue and you need to contact theme designer to resolve the issue if it is a theme done by you, revert the changes you did and we'll proceed with teh issue

solved...I have put this code into css custom code

.forum_search_wrap {  display: inline-block;  background-image: url(http:///...k/images/inputbg.gif);  background-repeat: repeat-x;  background-position: 0px 0px;  font-size: 0px;  line-height: 28px;  margin: 0px 0px 20px 0px;  padding: 0px 24px 0px 0px;  border-radius: 0px;  border-width: 0px;  -moz-border-radius: 3px;  -webkit-border-radius: 0px;  position: relative;  vertical-align: top;  background: #0f0f0f;}
body .forum_search_wrap input {  border: none;  background-image: none;  padding: 0px 0px 3px;  height: 20px;  color: #f0f0f0 !important;}

so i delete it

Alright thanks for letting us know.