Problem to format with of a particular field in a list 

Problem to format with of a particular field in a list 

  
I need to make a listview of messages, the body is a text field with 1000 characters.
What i want is to show this in a list as record of maximum 10 line of 100 charters (example) [like a timeline in social media apllications]
I'f  tried:
1)    > Limit the with of the the table cell in the listview to 100  ==> no effect on with in list
1a)  > I added s style to the body field in the screen > Text_Preformat   ==> no effect on with in list
             Text_Preformatted {
                  width: 500px;
                  white-space: -moz-pre-wrap;
                  white-space: pre;
                  word-wrap: break-word;
                  }
2)Changed the with proporty in the MeassageTable form 100% tot 100px   ==> no effect on with in list
What is the way to determine the with in a list??

thanks

Ron