The various parentheses that appear when you mouse-over the text are an epigraphy standard - the "Leiden parentheses system".
Their meanings are as follows:
[ ] - Reconstruction of missing/damaged parts of the monument
--- - A so called lacune or gap, an indeterminable number of glyphs missing
[.] - A determinable number of glyphs missing, denoted by the number of dots (in this case, one glyph is missing
( ) - Spelled out abbreviations, like for instance D M = D(is) M(anibus)
< > - Masons corrections or additions
{ } - Masons deletions of mistakes (double letters, upside down,...)
[[[ ]] - Reconstructed parts of the inscription that have been erased in antiquity (damnatio memoriae)
vvv - Empty space on the monument, each v represents the space of one glyph (in this case three) (v stands for vacat)
That's about it,...
As for the link, I stumbled onto this forum due to this thread, and the link is indeed interesting, especially to see some monuments and practice on them a bit, he he
The thing that irks me though, is the pronounciation and the fact that vixit is written out (and pronounced) as uixit.
Anyway, hopefully this will explain why and how the parentheses are used!