diff --git a/lib/less/browser.js b/lib/less/browser.js
index 310e5ce7..db6d77e6 100644
--- a/lib/less/browser.js
+++ b/lib/less/browser.js
@@ -146,11 +146,12 @@ function loadStyleSheet(sheet, callback, reload, remaining) {
 }
 
 function extractId(href) {
-    return href.replace(/^[a-z]+:\/\/?[^\/]+/, '')  // Remove protocol & domain
-               .replace(/^\//,                 '')  // Remove root /
-               .replace(/\?.*$/,               '')  // Remove query
-               .replace(/\.[^\/]+$/,           '')  // Remove file extension
-               .replace(/[^\w-]+/g,           '-'); // Replace illegal characters
+    return href.replace(/^[a-z]+:\/\/?[^\/]+/, '' )  // Remove protocol & domain
+               .replace(/^\//,                 '' )  // Remove root /
+               .replace(/\?.*$/,               '' )  // Remove query
+               .replace(/\.[^\.\/]+$/,         '' )  // Remove file extension
+               .replace(/[^\.\w-]+/g,          '-')  // Replace illegal characters
+               .replace(/\./g,                 ':'); // Replace dots with colons(for valid id)
 }
 
 function createCSS(styles, sheet, lastModified) {
diff --git a/lib/less/parser.js b/lib/less/parser.js
index e226285a..71ab995a 100644
--- a/lib/less/parser.js
+++ b/lib/less/parser.js
@@ -522,7 +522,7 @@ less.Parser = function Parser(env) {
                     var value;
 
                     if (input.charAt(i) !== 'u' || !$(/^url\(/)) return;
-                    value = $(this.entities.quoted) || $(this.entities.variable) || $(/^[-\w%@$\/.&=:;#+?]+/);
+                    value = $(this.entities.quoted) || $(this.entities.variable) || $(/^[-\w%@$\/.&=:;#+?]+/) || "";
                     if (! $(')')) throw new(Error)("missing closing ) for url()");
 
                     return new(tree.URL)((value.value || value instanceof tree.Variable)