ReferenceError: Can't find variable: getURLParam

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You're asking for the impossible. When a piece of code executes, you can see what side-effects result. When it's blocked, there's nothing to observe. Web pages will throw errors whether or not Ghostery is present at all, so even watching the Console isn't enlightening. You're going to get a lot of false positives.

That said, there's more we could be doing. It's a lot of work, and extremely time-consuming — want to help? Yes? Good. Keep reading.

All "bugs" are not created equal.

» Some are self-sufficient. They consist of a simple script call, or, perhaps, an iframe or one-pixel transparent image, that nothing else notices or cares about. These are "safe" to block.

» Some involve setup:

&lt;script&gt;<br />
<em>// client and campaign IDs go here</em><br />
&lt;/script&gt;<br />
&lt;script src=&quot;<em>whatever</em>&quot;&gt;&lt;/script&gt;

These, too, are "safe" to block.

» Some are declarative:

&lt;!-- import <em>tracking_function</em> --&gt;<br />
&lt;script src=&quot;<em>whatever</em>&quot;&gt;&lt;/script&gt;<br />
&lt;script&gt;<br />
<em>tracking_function</em>(&quot;client&quot, &quot;campaign&quot;);<br />
&lt;/script&gt;

This will log an error (but it usually has no ill effects!).

Competent scripting doesn't have issues:

&lt;!-- import <em>tracking_function</em> --&gt;<br />
&lt;script src=&quot;<em>whatever</em>&quot;&gt;&lt;/script&gt;<br />
&lt;script&gt;<br />
<strong>try {</strong><br />
<em>tracking_function</em>(&quot;client&quot, &quot;campaign&quot;);</br>
<strong>}<br />
catch(e) {</strong><br />
// oh well<br />
<strong>}</strong><br />
&lt;/script&gt;

You start to see problems when certain "Web 2.0" techniques are employed. (Unfortunately, that's becoming more commonplace.)

If all web authors followed well-documented best practices, there would be no complaints. Guess what? There's a lot of sh*tty JavaScript out there. It's written by lowest-bidder subcontractors ["we don't have to pay for their health care!"], and rushed into production without adequate testing ["QA cuts into our profits!"].

So, what's our beleaguered ghost supposed to do? If you say, "only block what's known to be safe," people will bitch that that doesn't go far enough, and pursue more aggressive alternatives. If you say, "implement surrogates for everything that might possibly cause something else to break," people will complain about poor performance.

The "squeaky wheel" approach focuses attention and resources where they're most needed. Keep reporting problems as you find them, and we'll do what we can to make your experience better.