You can use the iframe tag to insert any URL into your page.
Here is an example:
<iframe src="http://google.com/"></iframe>
Other attributes to add to your iframe can be found here: http://www.w3schools.com/tags/tag_iframe.asp
- height
- name
- sandbox
- seamless
- src
- srcdoc
- width
Edit 2: I misunderstood the original question. I assumed live 'pop up' meant an iframe in a modal window. What I now believe was intended is that it is a link that opens in a new window. If that is the case you want to structure your html as follows:
<a href="http://www.airmachinekettle.com" target="_blank">
<div class="portfolio-box-1 branding">
<div class="mask-1"></div>
<img src="images/air-machine-kettle.jpg" alt="">
<h6>Air Machine Kettle</h6>
<p>Web</p>
</div>
</a>
Edit 3: It looks like the question is evolving a bit. It is neither an iframe nor a new window that opens a URL rather a new window that opens a larger image. If that is the correct understanding then you want to do the following:
<a class="group1" href="http://lorempixel.com/output/abstract-q-c-640-480-10.jpg" target="_blank">
<div class="portfolio-box-1 branding">
<div class="mask-1"></div>
<img src="http://lorempixel.com/output/abstract-q-c-640-480-10.jpg" width="100" height="40">
<h6>Air Machine Kettle</h6>
<p>Web</p>
</div>
</a>
Edit 4: We've come full circle. What OP was really looking was actually a modal window that will open a larger image of the thumbnail that was clicked on.
Examples of modal windows or light boxes can be found here:
http://fancybox.net/home
http://www.lokeshdhakar.com/projects/lightbox2/