The following table shows which Unicode characters are treated as 
whitespace in browsers and per spec.


Hex   | IE8    Firefox  WebKit  Opera  ECMA262/Unicode 5.10
------+----------------------------------------------------
9     | 9      9        9       9      9
a     | 10     10       10      10     10
b     | 11     11       11      11     11
c     | 12     12       12      12     12
d     | 13     13       13      13     13
20    | 32     32       32      32     32
85    | 133                            133
a0    | 160    160      160            160
1680  | 5760            5760           5760
180e  |                 6158           6158
2000  | 8192   8192     8192           8192
2001  | 8193   8193     8193           8193 
2002  | 8194   8194     8194           8194 
2003  | 8195   8195     8195           8195 
2004  | 8196   8196     8196           8196 
2005  | 8197   8197     8197           8197 
2006  | 8198   8198     8198           8198 
2007  | 8199   8199     8199           8199 
2008  | 8200   8200     8200           8200 
2009  | 8201   8201     8201           8201 
200a  | 8202   8202     8202           8202 
200b  | 8203   8203                    
2028  | 8232   8232     8232           8232
2029  | 8233   8233     8233           8233
202f  | 8239            8239           8239
205f  |                 8287           8287
3000  | 12288  12288    12288          12288
feff  | 65279  65279                   
fffe  |        65534                   


Test case:
http://software.hixie.ch/utilities/js/live-dom-viewer/?%3Cscript%3E%0D%0Afor%20(var%20i%20%3D%201%3B%20i%20%3C%200xFFFF%3B%20%2B%2Bi)%0D%0Atry%20%7B%0D%0A%20eval(%22var%22%20%2B%20String.fromCharCode(i)%20%2B%20%22x%22%20%2B%20i%20%2B%20%22%3D%5C%22%5C%22%3Bw(x%22%20%2B%20i%20%2B%20%22%2B%22%20%2B%20i%20%2B%20%22)%22)%0D%0A%7D%20catch(e)%20%7B%0D%0A%7D%0D%0A%3C%2Fscript%3E