Field Input limit

Hi,
 
Im using jahia4.1.0_01_b6070.  When entering over 255 characters in the
links/files portlet description field (smalltext) I get a display issue
(shown below).  After 255 characters has been reached it inputs a <br>
and then completes the outstanding description.  Is it possible to put a
limit on the input field to stop an administrator inputting more than
255 characters in the description field?  Also where is the <br> being
generated from?
 
 
 
Kind Regards
 
Graham