How to check with Javascript if script can be loaded
<p>It's quite common for companies to block social networks by proxy. Now, if there is a "like" button on a page it needs a <code>script</code> (for instance, Facebook .js), but since the access is blocked, browser will try to load it for two minutes or so and thus the rest of the page won't load.</p>

<p>Is it possible to check with JavaScript whether some particular website is available and load a script only after that?</p>

<p>Let's say there are Facebook, Twitter and Google+ on the page, and Facebook and Twitter is blocked.</p>

<pre><code>&lt;script src="facebook-api.js"&gt;
&lt;script src="twitter-api.js"&gt;
&lt;script src="google-api.js"&gt;
</code></pre>

<p>Google+ won't load. What can we do in this situation?</p>
