Make the default for attr() use the min value for the prop if 0 isn't valid.

Author: tabatkins

css3-values/Overview.html

@@ -1522,17 +1522,19 @@ <h3 id=attr><span class=secno>8.3. </span> Attribute References: &lsquo;<a
 
    <dd>The attribute value will be interpreted as a CSS &lsquo;<code
     class=css>&lt;integer></code>&rsquo;. The default is &lsquo;<code
-    class=css>0</code>&rsquo;. The default should also be used if the
-    property in question only accepts integers within a certain range and the
-    attribute is out of range.
+    class=css>0</code>&rsquo;, or else the property's minimum value is
+    &lsquo;<code class=css>0</code>&rsquo; is not valid for the property. The
+    default should also be used if the property in question only accepts
+    integers within a certain range and the attribute is out of range.
 
    <dt>&lsquo;<a href="#number"><code class=css>number</code></a>&rsquo;
 
    <dd>The attribute value will be interpreted as a CSS &lsquo;<code
     class=css>&lt;number></code>&rsquo;. The default is &lsquo;<code
-    class=css>0.0</code>&rsquo;. The default should also be used if the
-    property in question only accepts numbers within a certain range and the
-    attribute is out of range.
+    class=css>0.0</code>&rsquo;, or else the property's minimum value is
+    &lsquo;<code class=css>0.0</code>&rsquo; is not valid for the property.
+    The default should also be used if the property in question only accepts
+    numbers within a certain range and the attribute is out of range.
 
    <dt>&lsquo;<code class=css>length</code>&rsquo;
 

css3-values/Overview.src.html

@@ -1079,13 +1079,13 @@ <h3 id="attr">
 
 		<dt>''integer''
 		<dd>The attribute value will be interpreted as a CSS ''&lt;integer>''.
-		The default is ''0''. The default should also be used if the property
+		The default is ''0'', or else the property's minimum value is ''0'' is not valid for the property. The default should also be used if the property
 		in question only accepts integers within a certain range and
 		the attribute is out of range.
 
 		<dt>''number''
 		<dd>The attribute value will be interpreted as a CSS ''&lt;number>''.
-		The default is ''0.0''. The default should also be used if the
+		The default is ''0.0'', or else the property's minimum value is ''0.0'' is not valid for the property. The default should also be used if the
 		property in question only accepts numbers within a certain
 		range and the attribute is out of range.