This is a Boolean value that controls whether the textual content is wrapped at the right hand window border or not.
If the value false is assigned to this property, then words will wrap as the page is drawn. This is good and is the way you would expect a browser to behave. The text will flow according to the space available.
If the value true is assigned to this property, the line of text will continue to the right until a <BR> or other block level tag is encountered. This will force the horizontal width of the page to be extremely large and the user will need to scroll furiously to be able to see the text and then scroll back again for the start of the next line.
Only use this if you plan to place line breaks at frequent intervals yourself and really do need to control the line breaks manually. The effect is as if you had placed <PRE> tags around the content of the cell, although the font may still be a proportional font rather than the monospaced font that <PRE> sets up by default.