A FIFA referee since 2003, Kassai hails from Tatabanya and has worked the 2007 FIFA U-20 World Cup where he served as referee for (2) matches. Kassai also served in the 2008 Summer Olympics and was the referee for the final between Nigeria and Argentina (report here), as well as serving in UEFA Euro 2008.
Kassai does have a lucky star shining on him (some would say it is the resedue of hard work - I am among them) as in 2007 he was assigned to the U-21 Eurpoean Championship Finals in the Netherlands, but had to decline, as noted above he was also asked to attend the 2007 FIFA U-20 World Cup.
Kassai is a travel agent by trade and in a notable moment he was criticized for sending off Lisbon's Simon Vukcevic in a Champion's League match after Vukcevic scored the equalizer. Some circles believe that Kassai is a book referee unable to bend the book when needed.
Here is what I could find regarding statistics:
So while at the helm of 47 matches, he had 140 cautions (~3 per match) and 5 send offs (~.1 per match). Again these are just numbers, but given the match breakdown, it would to me be a strong indicator militating AWAY from the opinion he is a book referee.
Note however, he is clearly not as experienced as the USA's last referee Frank De Bleeckere, but I would opine is clearly a up and coming star on the international scene.
This next match will be an interesting test of how high that star may climb.