diff --git a/modules/33acrossBidAdapter.js b/modules/33acrossBidAdapter.js
index 2ecab4013f9..8bb084a7aeb 100644
--- a/modules/33acrossBidAdapter.js
+++ b/modules/33acrossBidAdapter.js
@@ -27,8 +27,8 @@ function _createBidResponse(response) {
   }
 }
 
-function _isViewabilityMeasurable() {
-  return !_isIframe();
+function _isViewabilityMeasurable(element) {
+  return !_isIframe() && element !== null;
 }
 
 function _getViewability(element, topWin, { w, h } = {}) {
@@ -46,12 +46,16 @@ function _createServerRequest(bidRequest, gdprConsent) {
   const sizes = _transformSizes(bidRequest.sizes);
   const minSize = _getMinSize(sizes);
 
-  const viewabilityAmount = _isViewabilityMeasurable()
+  const viewabilityAmount = _isViewabilityMeasurable(element)
     ? _getViewability(element, utils.getWindowTop(), minSize)
     : NON_MEASURABLE;
 
   const contributeViewability = ViewabilityContributor(viewabilityAmount);
 
+  if (element === null) {
+    utils.logWarn(`Unable to locate element with id: '${bidRequest.adUnitCode}'`);
+  }
+
   /*
    * Infer data for the request payload
    */
@@ -90,7 +94,7 @@ function _createServerRequest(bidRequest, gdprConsent) {
         'version': '$prebid.version$'
       }]
     }
-  }
+  };
 
   // Finally, set the openRTB 'test' param if this is to be a test bid
   if (params.test === 1) {
diff --git a/src/utils.js b/src/utils.js
index 843c0c11c76..ce3897392c1 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -124,7 +124,7 @@ exports.transformAdServerTargetingObj = function (targeting) {
  * Read an adUnit object and return the sizes used in an [[728, 90]] format (even if they had [728, 90] defined)
  * Preference is given to the `adUnit.mediaTypes.banner.sizes` object over the `adUnit.sizes`
  * @param {object} adUnit one adUnit object from the normal list of adUnits
- * @returns {array[array[number]]} array of arrays containing numeric sizes
+ * @returns {Array.<number[]>} array of arrays containing numeric sizes
  */
 export function getAdUnitSizes(adUnit) {
   if (!adUnit) {
@@ -151,8 +151,8 @@ export function getAdUnitSizes(adUnit) {
 
 /**
  * Parse a GPT-Style general size Array like `[[300, 250]]` or `"300x250,970x90"` into an array of sizes `["300x250"]` or '['300x250', '970x90']'
- * @param  {array[array|number]} sizeObj Input array or double array [300,250] or [[300,250], [728,90]]
- * @return {array[string]}  Array of strings like `["300x250"]` or `["300x250", "728x90"]`
+ * @param  {(Array.<number[]>|Array.<number>)} sizeObj Input array or double array [300,250] or [[300,250], [728,90]]
+ * @return {Array.<string>}  Array of strings like `["300x250"]` or `["300x250", "728x90"]`
  */
 export function parseSizesInput(sizeObj) {
   var parsedSizes = [];
@@ -190,7 +190,7 @@ export function parseSizesInput(sizeObj) {
   }
 
   return parsedSizes;
-};
+}
 
 // parse a GPT style sigle size array, (i.e [300,250])
 // into an AppNexus style string, (i.e. 300x250)
@@ -199,7 +199,7 @@ export function parseGPTSingleSizeArray(singleSize) {
   if (exports.isArray(singleSize) && singleSize.length === 2 && (!isNaN(singleSize[0]) && !isNaN(singleSize[1]))) {
     return singleSize[0] + 'x' + singleSize[1];
   }
-};
+}
 
 /**
  * @deprecated This function will be removed soon. Use http://prebid.org/dev-docs/bidder-adaptor.html#referrers
@@ -215,7 +215,7 @@ exports.getTopWindowLocation = function() {
     if (loc) return parse(loc, {'decodeSearchAsString': true});
   }
   return exports.getWindowLocation();
-}
+};
 
 /**
  * @deprecated This function will be removed soon. Use http://prebid.org/dev-docs/bidder-adaptor.html#referrers
@@ -375,9 +375,9 @@ exports.getParameterByName = getParameterByName;
 
 /**
  * This function validates paramaters.
- * @param  {object[string]} paramObj          [description]
+ * @param  {Object} paramObj          [description]
  * @param  {string[]} requiredParamsArr [description]
- * @return {bool}                   Bool if paramaters are valid
+ * @return {boolean}                   Bool if paramaters are valid
  */
 exports.hasValidBidRequest = function (paramObj, requiredParamsArr, adapter) {
   var found = false;
@@ -439,11 +439,11 @@ exports.isNumber = function(object) {
 
 exports.isPlainObject = function(object) {
   return exports.isA(object, tObject);
-}
+};
 
 exports.isBoolean = function(object) {
   return exports.isA(object, tBoolean);
-}
+};
 
 /**
  * Return if the object is "empty";
@@ -669,8 +669,8 @@ exports.createTrackPixelIframeHtml = function (url, encodeUri = true, sandbox =
 
 /**
  * Returns iframe document in a browser agnostic way
- * @param  {object} iframe reference
- * @return {object}        iframe `document` reference
+ * @param  {Object} iframe reference
+ * @return {Object}        iframe `document` reference
  */
 exports.getIframeDocument = function (iframe) {
   if (!iframe) {
@@ -874,7 +874,7 @@ export function delayExecution(func, numRequiredCalls) {
  * @export
  * @param {array} xs
  * @param {string} key
- * @returns {${key_value}: ${groupByArray}, key_value: {groupByArray}}
+ * @returns {Object} {${key_value}: ${groupByArray}, key_value: {groupByArray}}
  */
 export function groupBy(xs, key) {
   return xs.reduce(function(rv, x) {
@@ -885,7 +885,7 @@ export function groupBy(xs, key) {
 
 /**
  * deepAccess utility function useful for doing safe access (will not throw exceptions) of deep object paths.
- * @param {object} obj The object containing the values you would like to access.
+ * @param {Object} obj The object containing the values you would like to access.
  * @param {string|number} path Object path to the value you would like to access.  Non-strings are coerced to strings.
  * @returns {*} The value found at the specified object path, or undefined if path is not found.
  */
@@ -905,7 +905,7 @@ export function deepAccess(obj, path) {
 
 /**
  * Returns content for a friendly iframe to execute a URL in script tag
- * @param {url} URL to be executed in a script tag in a friendly iframe
+ * @param {string} url URL to be executed in a script tag in a friendly iframe
  * <!--PRE_SCRIPT_TAG_MACRO--> and <!--POST_SCRIPT_TAG_MACRO--> are macros left to be replaced if required
  */
 export function createContentToExecuteExtScriptInFriendlyFrame(url) {
@@ -919,9 +919,9 @@ export function createContentToExecuteExtScriptInFriendlyFrame(url) {
 /**
  * Build an object consisting of only defined parameters to avoid creating an
  * object with defined keys and undefined values.
- * @param {object} object The object to pick defined params out of
+ * @param {Object} object The object to pick defined params out of
  * @param {string[]} params An array of strings representing properties to look for in the object
- * @returns {object} An object containing all the specified values that are defined
+ * @returns {Object} An object containing all the specified values that are defined
  */
 export function getDefinedParams(object, params) {
   return params
@@ -966,8 +966,8 @@ export function getBidderRequest(bidRequests, bidder, adUnitCode) {
 }
 /**
  * Returns user configured bidder params from adunit
- * @param {object} adunits
- * @param {string} adunit code
+ * @param {Object} adUnits
+ * @param {string} adUnitCode code
  * @param {string} bidder code
  * @return {Array} user configured param for the given bidder adunit configuration
  */
@@ -1002,7 +1002,7 @@ const compareCodeAndSlot = (slot, adUnitCode) => slot.getAdUnitPath() === adUnit
 
 /**
  * Returns filter function to match adUnitCode in slot
- * @param {object} slot GoogleTag slot
+ * @param {Object} slot GoogleTag slot
  * @return {function} filter function
  */
 export function isAdUnitCodeMatchingSlot(slot) {
@@ -1041,9 +1041,9 @@ export function unsupportedBidderMessage(adUnit, bidder) {
  * @return {Object} object
  */
 export function deletePropertyFromObject(object, prop) {
-  let result = Object.assign({}, object)
+  let result = Object.assign({}, object);
   delete result[prop];
-  return result
+  return result;
 }
 
 /**
@@ -1081,7 +1081,7 @@ export function convertCamelToUnderscore(value) {
  * normally read from bidder params
  * eg { foo: ['bar', 'baz'], fizz: ['buzz'] }
  * becomes [{ key: 'foo', value: ['bar', 'baz']}, {key: 'fizz', value: ['buzz']}]
- * @param {Object{Arrays}} keywords object of arrays representing keyvalue pairs
+ * @param {Object} keywords object of arrays representing keyvalue pairs
  * @param {string} paramName name of parent object (eg 'keywords') containing keyword data, used in error handling
  */
 export function transformBidderParamKeywords(keywords, paramName = 'keywords') {