CSS float right weird behaviour - html

Question

I have 2 threads in an imageboard stacked on top of each other, each thread has some text and an image file.
I want images to be always on right of the thread, instead of being on top of reply button.
When I float image to right by float: right; the images keep stacking on top of each other instead and form a branch like structure
How do I force images with post-image class to not break <div> structure of following thread and stay on right of screen?
<div class="you" id="thread_27" data-board="b" align="Right">
<div class="files">
<div class="file">
<p class="fileinfo">File: 1454704253855.jpg <span class="unimportant">(78.69 KB, 1024x768, <span class="postfilename">soft-color-background.jpg</span>)</span>
</p>
<img class="post-image" src="/b/thumb/1454704253855.png" style="width: 255px; height: 192px; max-width: 98%;" alt="">
</div>
</div>
<div class="post op" id="op_27">
<p class="intro">
<input class="delete" name="delete_27" id="delete_27" type="checkbox">
<label for="delete_27"><span class="name">Anonymous (You)</span>
<time data-local="true" datetime="2016-02-05T20:30:54Z">02/05/16 (Fri) 22:30:54</time>
</label> <a class="post_no" id="post_no_27" onclick="highlightReply(27)" href="/b/res/27.html#27">No.</a><a class="post_no" onclick="citeReply(27)" href="/b/res/27.html#q27">27</a>[Reply]</p>
<div class="body">xxxxxx2</div>
</div>
<br class="clear">
<hr>
</div>
<div class="you" id="thread_26" data-board="b" align="Right">
<div class="files">
<div class="file">
<p class="fileinfo">File: 1454704190918.jpg <span class="unimportant">(157.33 KB, 1024x768, <span class="postfilename" title="mac-style-presentation-background.jpg">mac-style-presentation-bac….jpg</span>)</span>
</p>
<img class="post-image" src="/b/thumb/1454704190918.png" style="width: 255px; height: 192px; max-width: 98%;" alt="">
</div>
</div>
<div class="post op" id="op_26">
<p class="intro">
<input class="delete" name="delete_26" id="delete_26" type="checkbox">
<label for="delete_26"><span class="name">Anonymous (You)</span>
<time data-local="true" datetime="2016-02-05T20:29:51Z">02/05/16 (Fri) 22:29:51</time>
</label> <a class="post_no" id="post_no_26" onclick="highlightReply(26)" href="/b/res/26.html#26">No.</a><a class="post_no" onclick="citeReply(26)" href="/b/res/26.html#q26">26</a>[Reply]</p>
<div class="body">xxxxx</div>
</div>
<br class="clear">
<hr>
</div>
when I add CSS
.post-image
{
float: right;
}
it breaks everything.
jsfiddle before
js fiddle after floating post-image to the right

Answer 1

This happens because of float left or right. clear controls the float behavior hence, the ideal way is to make all the float properties inside a container usually div. Sometimes, browser renders it differently so whenever coming to a new container or sibling, ideal way is to clear the float(if you don't need the floating property).
In your code you could probably
Add this:
.clear{
clear:both;
}
to better understand. Also don't forget to play with it to put it ideally where it is required.

Answer 2

If you can use flexbox (no way to old browsers) try something like:
.row{
display: flex;
flex-direction: row;
flex-wrap: nowrap;
justify-content: flex-start;
align-content: stretch;
align-items: flex-start;
}
.col1{
position: relative;
flex: 1 1 100%;
align-self: stretch;
overflow: hidden;
}
.col2{
position: relative;
display: flex;
flex-direction: column;
flex: 0 1 45px;
align-self: stretch;
}
on a html strukture like
<div class="row">
<div class="col1">
</div>
<div class="col2">
</div>
</div>

Answer 3

Add one more div with "clear: both" styling will fix your problem.
<div class="file">
your code here...
<div style="clear:both"></div>
</div>
jsfiddle