vbulletin screwing up custom input CSS

[DionDev]

my custom input css is as follows:

.topinput {
  background-image: url(images/top_inputbg.gif);
  height: 22px;
  font-family: verdana;
  font-size: 8pt;
  color: #8b8b8b;
  width: 145px;
  border: 1px solid #dddddd;
  padding: 3px 0px 3px 9px;
}

2 inputs use this class. the problem is, on my normal site these inputs look the way theyre supposed to, on vbulletin theyre all messed up.

why is this happening?