Unicode space characters (hopefully) sorted by their widths:

200b |​| ¹
200c |‌| ¹
200d |‍| ¹
2060 |⁠| ¹
feff || ¹²
200a | |
2006 | |
2007 | |
2009 | |
202f | | ²
205f | |
2005 | |
0020 | |
00a0 | | ²
2008 | |
2004 | |
2000 | |
2002 | |
2007 | |
2001 | |
2003 | |
3000 |　|

¹ Zero-width
² No-break

Use them like this in HTML: e.g. |　| becomes |　|.