diff --git a/css-doodle.js b/css-doodle.js
index 4f245ce..dd4b1f0 100644
--- a/css-doodle.js
+++ b/css-doodle.js
@@ -303,15 +303,26 @@ const is = {
 };
 
 function iterator(input) {
-  let index = 0;
+  let index = 0, col = 1, line = 1;
   return {
     curr:  (n = 0) => input[index + n],
-    next:  () => input[index++],
     end:   () => input.length <= index,
-    index: () => index
+    info:  () => ({ index, col, line }),
+    next:  () => {
+      let next = input[index++];
+      if (next == '\n') line++, col = 0;
+      else col++;
+      return next;
+    }
   };
 }
 
+function throw_error(msg, { col, line }) {
+  throw new Error(
+    `(at line ${ line }, column ${ col }) ${ msg }`
+  );
+}
+
 function skip_block(it) {
   let [skipped, c] = [it.curr(), it.curr()];
   let is_close_bracket = is.close_bracket_of(c);
@@ -336,7 +347,7 @@ function read_property(it) {
   while (!it.end()) {
     if ((c = it.curr()) == ':') break;
     else if (!/[a-zA-Z\-]/.test(c)) {
-      throw new Error('Syntax error: Bad property name.');
+      throw_error('Syntax error: Bad property name.', it.info());
     }
     else if (!is.white_space(c)) prop += c;
     it.next();
@@ -417,6 +428,9 @@ function read_value(it) {
       value.push(read_func(it));
     }
     else if (!is.white_space(c) || !is.white_space(it.curr(-1))) {
+      if (c == ':') {
+        throw_error('Syntax error: Bad property name.', it.info());
+      }
       text.value += c;
     }
     it.next();
@@ -533,10 +547,6 @@ function compile(input, size) {
   return generator(tokenizer(input), size);
 }
 
-function clamp(num, min, max) {
-  return (num <= min) ? min : ((num >= max) ? max : num);
-}
-
 function parse(size) {
   const split = (size + '')
     .replace(/\s+/g, '')
@@ -553,6 +563,10 @@ function parse(size) {
   };
 }
 
+function clamp(num, min, max) {
+  return (num <= min) ? min : ((num >= max) ? max : num);
+}
+
 class Doodle extends HTMLElement {
   constructor() {
     super();
diff --git a/src/parse-size.js b/src/parse-size.js
index 93171b9..4481250 100644
--- a/src/parse-size.js
+++ b/src/parse-size.js
@@ -1,7 +1,3 @@
-function clamp(num, min, max) {
-  return (num <= min) ? min : ((num >= max) ? max : num);
-}
-
 export default function parse(size) {
   const split = (size + '')
     .replace(/\s+/g, '')
@@ -17,3 +13,7 @@ export default function parse(size) {
     count: ret.x * ret.y
   };
 }
+
+function clamp(num, min, max) {
+  return (num <= min) ? min : ((num >= max) ? max : num);
+}
diff --git a/src/tokenizer.js b/src/tokenizer.js
index 7de3fd8..c0ed153 100644
--- a/src/tokenizer.js
+++ b/src/tokenizer.js
@@ -29,15 +29,26 @@ const is = {
 };
 
 function iterator(input) {
-  let index = 0;
+  let index = 0, col = 1, line = 1;
   return {
     curr:  (n = 0) => input[index + n],
-    next:  () => input[index++],
     end:   () => input.length <= index,
-    index: () => index
+    info:  () => ({ index, col, line }),
+    next:  () => {
+      let next = input[index++];
+      if (next == '\n') line++, col = 0;
+      else col++;
+      return next;
+    }
   };
 }
 
+function throw_error(msg, { col, line }) {
+  throw new Error(
+    `(at line ${ line }, column ${ col }) ${ msg }`
+  );
+}
+
 function skip_block(it) {
   let [skipped, c] = [it.curr(), it.curr()];
   let is_close_bracket = is.close_bracket_of(c);
@@ -62,7 +73,7 @@ function read_property(it) {
   while (!it.end()) {
     if ((c = it.curr()) == ':') break;
     else if (!/[a-zA-Z\-]/.test(c)) {
-      throw new Error('Syntax error: Bad property name.');
+      throw_error('Syntax error: Bad property name.', it.info());
     }
     else if (!is.white_space(c)) prop += c;
     it.next();
@@ -143,6 +154,9 @@ function read_value(it) {
       value.push(read_func(it));
     }
     else if (!is.white_space(c) || !is.white_space(it.curr(-1))) {
+      if (c == ':') {
+        throw_error('Syntax error: Bad property name.', it.info());
+      }
       text.value += c;
     }
     it.next();