html posts wont work

i have read most of the guides on html codes for adding flashes and an arcade section .
i have followed these but believe that i have made a mistake ,as post look fine and correct when previewed but fail to work when posted and leave nothing but code when finally posted .

any through guides to adding html step by step . or an idea on where i have gone wrong
any and all help will be appreciated . tanx

try activate your HTML option

ACP > User & Groups > User setting > allow HTML > yes

dont forget to look to your own profile

preferences > Always allow HTML > set it to 'YES'