Problem with posts

Hello. I dont know how to describe my problem so that you can understand it
but I will give it a try.

When someone writes a post in my forum, if he/she doesnt press the enter button
to go to the next line but instesd continue writing till the line cganges automatically,
when the post is submited my whole forum's width changes.
It expands!

I hope you understood because I could really use some help here!

r u using any html tags there. if yes let me know. because i was also having same problem while using html tags.

I am using a html tag in the homepage message..

bump

Please help it is really important!