Cant Change Column width in Zen CSS

hello,
as I'm a newbie to Drupal i'd really appreciate if i could help from experts regarding Drupal Theming.

I'm using Zen-Fixed as my website theme and have been able to modify Primary Links (Looks and Position),
could change center column width as well but when it comes to changing the width of Left and RIght sidebard i'm stuck.. any change in margin or width is causing the entire layout to collapse.

I need to 3 columns of same width in my site and if theres anyone who knows (I'm sure many of u do) plz plz explain it to me... i'm not a new biw to HTML, CSS and PHP but all my experience is proving to be useless in this case...

Guys HELP MEEE..............
the css is as given below

/* $Id: layout.css,v 1.5.2.1 2007/01/17 05:28:41 jjeff Exp $ */

/**
*  LAYOUT STYLES
*
*  Define CSS classes to create a table-free,
*  3-column, 2-column, or single column layout 
*  depending on whether blocks are enabled in the 
*  left or right columns.
*/

/**
 * Layout
 */

#container {
  margin: 0 auto;
  /*padding: 0 20px;*/
  max-width: 1270px;
background-color: #999;
}

/* With 3 columns, require a minimum width of 1000px to ensure there is enough horizontal space. */
body.both-sidebars {
  /*min-width: 980px;*/

}
/* With 2 columsn, require a minimum width of 800px. */
body.sidebar-left, body.sidebar-right {
  /*min-width: 780px;*/

}

/* We must define 100% width to avoid the body being too narrow for near-empty pages */
/* Background White One */
#main {
  float: left;
  width: 100%;
  background-color: #fff;
}

/* So we move the #main container over the sidebars to compensate */
body.sidebar-left #main {
  margin-left: -210px;

}
body.sidebar-right #main {
  margin-right: -210px;
}

body.both-sidebars #main {
  margin: 0px -210px;
}

#squeeze {
  position: relative;
  padding: 0 1em;
  background-color: #D1EAFC;
}

/* And add blanks left and right for the sidebars to fill */
body.sidebar-left #squeeze {
  margin-left: 210px;
}
body.sidebar-right #squeeze {
  margin-right: 210px;
}

/* Change 250 px to a different value to increase or decrease :IMP will work when both the sidebars are enabled */
body.both-sidebars #squeeze {
  margin: 0 260px;
}

/* We ensure the sidebars are still clickable using z-index */
#container .sidebar {
  margin: 0 0 0;
  width: 210px;
  float: left;
  z-index: 2;
  position: relative;
}

#container .sidebar .block {
  margin: 0 0 1.5em 0;
background-color: #666; 
}

#sidebar-left .block {
  padding: 0 15px 0 0px;

}

#sidebar-right .block {
  padding: 0 0px 0 15px;
}

.block .content {
  margin: 0.5em 0;
background-color: #ccc; 
}

#footer {
  float: none;
  clear: both;
  margin: 4em 0 -3em;
}


/*
body.sidebar-left  #footer {
  margin-left: -210px;
}

body.sidebar-right #footer {
  margin-right: -210px;
}

body.both-sidebars #footer {
  margin: 0 -210px;
}