For Bootstrap 3.0 or higher, see this answer
We're only looking at class .span1
here (one column on a 12 wide grid), but you can achieve what you want by removing the left margin from:
.row-fluid [class*="span"] { margin:0 } // line 571 of bootstrap responsive
Then changing .row-fluid .span1
's width to equal to 100% divided by 12 columns (8.3333%).
.row-fluid .span1 { width: 8.33334% } // line 632 of bootstrap responsive
You may want to do this by adding an additional class that would allow you to leave the base grid system intact:
.row-fluid [class*="NoGutter"] { margin-left:0 }
.row-fluid .span1NoGutter { width: 8.33334% }
<div class="row-fluid show-grid">
<div class="span1NoGutter">1</div>
</div>
You could repeat this pattern for all other columns, as well:
.row-fluid .span2NoGutter { width:16.66667%; margin-left:0 } // 100% / 6 col
.row-fluid .span4NoGutter { width:25%; margin-left:0 } // 100% / 4 col
.row-fluid .span3NoGutter { width:33.33333%; margin-left:0 } // 100% / 3 col
or
.row-fluid .span4NoGutter { width:25% }
.row-fluid [class*="NoGutter"] { margin-left:0 }
* EDIT (insisting on using the default grid)
If the default grid system is a requirement, it defaults to a width of 940px (the .container and .span12 classes, that is); thus, in simplest terms, you'd want to divide 940 by 12. That equates to 12 containers 78.33333px wide.
So line 339 of bootstrap.css could be edited like so:
.span1 { width:78.33333px; margin-left:0 }
or
.span1 { width:8.33334%; margin-left:0 }
// this should render at 78.333396px (78.333396 x 12 = 940.000752)