sass compiler has generated two css files and i can only attach one css into the index.html

Here, I got style.scss

$myColor: #009a82;
$myString: " some text here ";
$myFontSize: 13px;
$myMargin: 0px auto;
$myWidth: 460px;

h1 {
    color: $myColor;
    margin: 0;
    padding: 0;
}

#container {
    width: $myWidth;
    margin: $myMargin;
}

I can get a css file:

h1 {
  color: #009a82;
  margin: 0;
  padding: 0; }

#container {
  width: 460px;
  margin: 0px auto; }

I got :

/*
Error: Invalid property: "Backtrace:" (no value).
        on line 4 of Sass

1: /*
2: Errno::ENOENT: No such file or directory @ rb_sysopen - Sass
3: 
4: Backtrace:
5: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:482:in `read'
6: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:482:in `update_stylesheet'
7: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:215:in `block in update_stylesheets'
8: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `each'
9: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `update_stylesheets'

Backtrace:
Sass:4
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:719:in `parse_property'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:681:in `parse_property_or_rule'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:647:in `parse_line'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:525:in `build_tree'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:544:in `block in append_children'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:543:in `each'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:543:in `append_children'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:396:in `_to_tree'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:368:in `_render_with_sourcemap'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/engine.rb:285:in `render_with_sourcemap'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:490:in `update_stylesheet'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:215:in `block in update_stylesheets'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `each'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `update_stylesheets'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:293:in `watch'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin.rb:108:in `method_missing'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/exec/sass_scss.rb:370:in `watch_or_update'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/exec/sass_scss.rb:50:in `process_result'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/exec/base.rb:52:in `parse'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/exec/base.rb:19:in `parse!'
C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/bin/sass:13:in `<top (required)>'
C:/Ruby21/bin/sass:23:in `load'
C:/Ruby21/bin/sass:23:in `<main>'
*/
body:before {
  white-space: pre;
  font-family: monospace;
  content: "Error: Invalid property: "Backtrace:" (no value).A         on line 4 of SassA A 1: /*A 2: Errno::ENOENT: No such file or directory @ rb_sysopen - SassA 3: A 4: Backtrace:A 5: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:482:in `read'A 6: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:482:in `update_stylesheet'A 7: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:215:in `block in update_stylesheets'A 8: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `each'A 9: C:/Ruby21/lib/ruby/gems/2.1.0/gems/sass-3.4.9/lib/sass/plugin/compiler.rb:209:in `update_stylesheets'"; }

Try it like this

margin: 0 (-$pad) 20px (-$pad);

I'm in the same boat (beginner to Sass/Compass) and had to do something similar. Here's what I came up with, using nested lists:

$flash_types: (success #d4ffd4) (error #ffd5d1);

@each $flash_def in $flash_types {
    $type: nth($flash_def, 1);
    $colour: nth($flash_def, 2);

    &.#{$type} {
        background-color: $colour;
        background-image: url(../images/#{$type}.png);
    }
}