diff --git a/TODO.txt b/TODO.txt
index 70358cf7..f41cbd9a 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -6,4 +6,7 @@ Primary:
 
 Code issues:
  - Rename AbstractTest to Harness
- - (?) Create a TokenFactory to prevent really long lines
\ No newline at end of file
+ - (?) Create a TokenFactory to prevent really long lines
+
+Enhancements:
+ - Do fixes for Firefox's inability to handle COL alignment props (Bug 915)
\ No newline at end of file
diff --git a/library/HTMLPurifier/AttrDef/NumberSpan.php b/library/HTMLPurifier/AttrDef/NumberSpan.php
new file mode 100644
index 00000000..9ff6de4f
--- /dev/null
+++ b/library/HTMLPurifier/AttrDef/NumberSpan.php
@@ -0,0 +1,23 @@
+<?php
+
+require_once 'HTMLPurifier/AttrDef.php';
+
+// for col and row spans, essentially, a positive integer
+class HTMLPurifier_AttrDef_NumberSpan extends HTMLPurifier_AttrDef
+{
+    
+    function validate($string) {
+        
+        $string = trim($string);
+        if ($string === '') return false;
+        if ($string === '1') return false; // this is the default value
+        if (!is_numeric($string)) return false;
+        $int = (int) $string;
+        if ($int <= 0) return false;
+        return (string) $int;
+        
+    }
+    
+}
+
+?>
\ No newline at end of file
diff --git a/library/HTMLPurifier/Definition.php b/library/HTMLPurifier/Definition.php
index 60f48a36..b76b270c 100644
--- a/library/HTMLPurifier/Definition.php
+++ b/library/HTMLPurifier/Definition.php
@@ -9,6 +9,7 @@ require_once 'HTMLPurifier/AttrDef.php';
     require_once 'HTMLPurifier/AttrDef/Pixels.php';
     require_once 'HTMLPurifier/AttrDef/Length.php';
     require_once 'HTMLPurifier/AttrDef/MultiLength.php';
+    require_once 'HTMLPurifier/AttrDef/NumberSpan.php';
 require_once 'HTMLPurifier/AttrTransform.php';
     require_once 'HTMLPurifier/AttrTransform/Lang.php';
     require_once 'HTMLPurifier/AttrTransform/TextAlign.php';
@@ -290,17 +291,26 @@ class HTMLPurifier_Definition
         $this->info['table']->attr['border'] = new HTMLPurifier_AttrDef_Pixels();
         
         $e_Length = new HTMLPurifier_AttrDef_Length();
-        $this->info['table']->attr['cellpadding'] = $e_Length;
-        $this->info['table']->attr['cellspacing'] = $e_Length;
-        $this->info['table']->attr['width'] = $e_Length;
-        $this->setAttrForTableElements('charoff', $e_Length);
-        $this->info['img']->attr['height'] = $e_Length;
+        $this->info['table']->attr['cellpadding'] =
+        $this->info['table']->attr['cellspacing'] =
+        $this->info['table']->attr['width'] =
+        $this->info['img']->attr['height'] =
         $this->info['img']->attr['width'] = $e_Length;
+        $this->setAttrForTableElements('charoff', $e_Length);
         
         $e_MultiLength = new HTMLPurifier_AttrDef_MultiLength();
-        $this->info['col']->attr['width'] = $e_MultiLength;
+        $this->info['col']->attr['width'] =
         $this->info['colgroup']->attr['width'] = $e_MultiLength;
         
+        $e__NumberSpan = new HTMLPurifier_AttrDef_NumberSpan();
+        $this->info['colgroup']->attr['span'] =
+        $this->info['col']->attr['span']   =
+        $this->info['td']->attr['rowspan'] =
+        $this->info['th']->attr['rowspan'] = 
+        $this->info['td']->attr['colspan'] =
+        $this->info['th']->attr['colspan'] = $e__NumberSpan;
+        
+        
         //////////////////////////////////////////////////////////////////////
         // UNIMP : info_tag_transform : transformations of tags
         
diff --git a/tests/HTMLPurifier/AttrDef/NumberSpanTest.php b/tests/HTMLPurifier/AttrDef/NumberSpanTest.php
new file mode 100644
index 00000000..bb9c3050
--- /dev/null
+++ b/tests/HTMLPurifier/AttrDef/NumberSpanTest.php
@@ -0,0 +1,28 @@
+<?php
+
+require_once 'HTMLPurifier/AttrDefHarness.php';
+require_once 'HTMLPurifier/AttrDef/NumberSpan.php';
+
+class HTMLPurifier_AttrDef_NumberSpanTest extends HTMLPurifier_AttrDefHarness
+{
+    
+    function test() {
+        
+        $this->def = new HTMLPurifier_AttrDef_NumberSpan();
+        
+        // this one requires a little explanation. A colspan="1" shouldn't
+        // exist at all: it's just a dud, since the default value is already
+        // supplied
+        $this->assertDef('1', false);
+        
+        $this->assertDef('4');
+        $this->assertDef('4.5', '4'); // round down (truncate)
+        $this->assertDef('0', false);
+        $this->assertDef('-4', false);
+        $this->assertDef('asdf', false);
+        
+    }
+    
+}
+
+?>
\ No newline at end of file
diff --git a/tests/HTMLPurifier/Strategy/ValidateAttributesTest.php b/tests/HTMLPurifier/Strategy/ValidateAttributesTest.php
index d56152ef..51685754 100644
--- a/tests/HTMLPurifier/Strategy/ValidateAttributesTest.php
+++ b/tests/HTMLPurifier/Strategy/ValidateAttributesTest.php
@@ -80,6 +80,9 @@ class HTMLPurifier_Strategy_ValidateAttributesTest extends
         <td abbr="carrot">Carrot Humungous</td>
         <td>$500.23</td>
     </tr>
+    <tr>
+        <td colspan="2">Taken off the market</td>
+    </tr>
 </table>
 HTML;
         $expect[13] = $inputs[13];
diff --git a/tests/index.php b/tests/index.php
index fc326706..31ebb57a 100644
--- a/tests/index.php
+++ b/tests/index.php
@@ -45,6 +45,7 @@ $test_files[] = 'AttrDef/TextTest.php';
 $test_files[] = 'AttrDef/LangTest.php';
 $test_files[] = 'AttrDef/PixelsTest.php';
 $test_files[] = 'AttrDef/LengthTest.php';
+$test_files[] = 'AttrDef/NumberSpanTest.php';
 $test_files[] = 'IDAccumulatorTest.php';
 $test_files[] = 'TagTransformTest.php';
 $test_files[] = 'AttrTransform/LangTest.php';