Page lost format?

Hello

I am a new customer to IPB, not sure if i got it right.

I am using page with category, so i put it into menu. I am trying use page function as wiki, so i prepared text for main page.

If I open with link with record, i got full text. if i open with category link, my page lost format.

Below is what i want

and Below is what i got

Anyone knows how it happen? any input would be appreciated!

Thanks!

John