Hi Yusuf i take a look and follow this steps:
1 - Access through ftp/cpanel and edit this archive - sep1/media/cck/css/cck.search.css.
2 - You will need to remove the float:left style inside this css selector: div.cck_forms.cck_search div.cck_form or near the line 84. After do this, your buttons will be center align.
3 - Inside your css archive, create this above rule:
#art_title_backend {
width: 98%;
}
This will change the width of your search input, keeping all the elements align.