My forum font size have change

[business]

haloo, i just wondering, i add my header in my website as you seen in this topic:

http://www.simplemachines.org/community/index.php?topic=72802.0

but why my font size change? just like you see in
hxxp:www.businesseducationsite.com/smf/ [nonactive]
is there any syntax i accidently delete?
Please help me, what when wrong with my forum?