firefox addon - XUL element to break line -

i define label , set value

<bbox>   <label id="notify" value="test"/> </bbox> 

the width of label fix if value (text) longer width want line break. tried css doing

word-wrap:break word;  

but not work. there xul element provides such feature or know other technique?

you can either <label> or <description> element, need use textcontent rather value.

<label id="notify">test</label>