See Template:Hidden text.
Usage
Use this template to create a space (not an actual selectable space) equal in width to what its argument would be if rendered. All spaces, both before, within, and following the single argument are significant, although as in normal wikitext multiple consecutive spaces are collapsed into a single space. Use if you need to represent multiple spaces.
Example
foo{{Hidden text|oooooooooo}}bar produces
foobar