We can just use isNaN for this check in the IE opacity code.

diff --git a/src/css.js b/src/css.js
index b9a1c52..77949ae 100644 (file)
--- a/src/css.js
+++ b/src/css.js
@@ -187,7 +187,7 @@ if ( !jQuery.support.opacity ) {
                        style.zoom = 1;
 
                        // Set the alpha filter to set the opacity
-                       var opacity = parseInt( value, 10 ) + "" === "NaN" ?
+                       var opacity = isNaN(value) ?
                                "" :
                                "alpha(opacity=" + value * 100 + ")";