What is the point of using absolute positioning in CSS?

this one helps. I my experience using absolute positioning works well on elements you are in 100% control of in terms of size; like a logo, a meny, rss links and things like this. Then you can place these elements exactly where you want them.
I prefer using float when I am displaying dynamic content on a page, since the size of the element can change, and the placement of all elements in relation works really good with floats. Just remember to clear the floats when needed!

it should still fix some issue When you apply positioning to an element, it will use the positioning available on it's parents. If none is provided, it will position to the body element. So when you position: absolute to get the text/link at the bottom of the element, you have to position: relative (or position: absolute) one of it's parents, otherwise it won't know which you want it to position in relation to. Conversely, whichever it finds first, it will use that element to position against.
I think it's possible you've got too much markup to accomplish what you're doing here (what is the .placeholder for? why not just use the li?), and the spans that wrap one of the blocks looks out of place (and should be a div if you really need a wrapper there). And I'm not sure, but you might want to change #items to a class, if you need to reuse it. It looks out of place as an id. And your id and class names are not descriptive, and your selectors are not specific enough (generally, stay away from ul and li for styling specific parts of a page, as these have a global effect).

<li>
    <div class="itemplaceholder">
        <img src="http://www.els.qut.edu.au/blendedlearning/blackboard/graphics/test_on.gif"/>
        <p>
            Test title<br/>
            Description A
            <a href="#">Link</a>
        </p>
    </div>
</li>

#items {
    display: inline;
    position:relative;
    margin: 0;
    padding: 0;
}
#items li {
    float: left;
    list-style-type: none;
    margin: 0;
    padding: 5px 0 0 0;
}
#items .itemplaceholder {
    height:200px;
    width:160px;
    text-align: center;
    position: relative;
}
.placeholder {
    width:640px;
    height:200px;
    overflow: hidden;
}
.content {
    width:800px;
    height:240px;
}
#items .itemplaceholder p {
    position: absolute;
    bottom: 5px;
    width: 100%;
    height: 50%;
}
#items .itemplaceholder p a {
    position: absolute;
    display: block;
    bottom: 0;
    text-align: center;
    width: 100%;
}

I wish this helpful for you Think about this. Even if you supply a singe font for your application, it will be rendered differently on different OSs, it can even be rendered differently on the same OS under different DPI.
Layout managers are your protection against these problems, sure, when you first start using them, they seem to get in the way, but once you get use to them, you'll never want to do without (try coding in VB and tell me otherwise)

seems to work fine You should just be able to use left:100% on your absolute positioned span element. I think this is the result you wanted. Also, I fixed your HTML by adding the closing tag for the first element.

#main {
  position: relative;
  display: inline-block;
}
#sub {
  position: absolute;
  bottom: 0;
  min-width: fit-content;
  left: 100%;
  background-color: orange;
}

<div id="main">
  <span>hello everyone.</span>
  <span id="sub">-Name</span>
</div>