css width, height for iexplorer working on firefox

in my style.css i have for example this, and it work fine in iexplorer but when i move to firefox the style is lost and i got the error shown below.

#header {
 width: 900px;
 position: relative;
 height: 170px;
 padding: 0;
 font-size: 14px;
 color: #000;
}

ERROR: from error console in firefox (sorry my local conf is in spanish i dont know how to translate it properly).

Advertencia: Error al interpretar el val开发者_开发知识库or para 'width'. Declaración rechazada. Archivo de origen: http://localhost:8080/cancilleria2008/css/estilos.css Línea: 1990

If somebody can explain me how to correct this i would really apreciate.

This css code appears to be fine, at least for me. Are you sure that the error is in this piece of your stylesheet?