Help-how to fix the table width to 800 pix in post new thread

[sellbuydomain]

sorry, i guess have to be member to post a new thread in order to see it. yes, i change the forum table to 800 pix instead of 100% in stylevars, i add some new simile icons there, i think this big similes expend the post new thread box to bigger than 800 width. i am trying to fix this table box to 800 width, the table box i am talking about is that post new thread box with all smilie icons can shoose from, now this box is bigger than 800 width, how do i change the post new thread or replied post box to 800, can you check it for me? or please register a user, and start to post a new thread, and you will know what i am trying to destribe, thank you for help