Callibre made no difference.
The HTML code underneath will sometimes make the kindle freeze when browsing. It will freeze around the tag <h4>PROBLEM</h4>. If searching for Problem and going to the location the kindle will freeze. I can't see whats wrong with the code, but its prett certantly something with the tables, because removing them eliminates the freezing.
Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/REC-html40/loose.dtd">
<html>
<head>
<title>Title</title>
<link rel="stylesheet" type="text/css" href="style_any.css">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<h5>Systemic Associations</h5>
<p>Text goes here.</p>
<h5>Pathology</h5>
<p>Text goes here.</p>
<h5>Treatment</h5>
<p>Text goes here.</p>
<h4>HEADING 4</h4>
<p>Text is here.</p>
<div>
<table>
<tr>
<td><img src="f044-5gr12.jpg" alt="#########"><br></td>
</tr>
<tr>
<td><img src="images/blank.gif" width="1" height="10" border="0" alt="#########"></td>
</tr>
<tr>
<td>
<p>Fig. 4-20 <span class="figure-caption"><b>Fig text. </b> Additional fig text..</span></p>
</td>
<td><img src="images/blank.gif" width="10" height="1" border="0" alt="#########"></td>
</tr>
</table>
</div>
<br>
<h4>Heading</h4>
<p>Text is here.</p>
<h4>HEDING 4</h4>
<p>Text is here.</p>
<h4>HEADING 4</h4>
<h5>Epidemiology and Pathogenesis</h5>
<p>Text here</p>
<h5>Manifestations</h5>
<p>Text here.</p>
<h5>Differential Diagnosis</h5>
<p>Text here</p>
<h5>Pathology</h5>
<p>Text here<sup></sup></p>
<h5>Treatment</h5>
<p>Text here</p>
<h4>REFERENCES</h4>
Text here
<br>
<hr>
<h2>Chapter 4 heading</h2>
<b>Authors</b><b></b>
<table cellpadding="4" cellspacing="0" style="border: 1px solid black;">
<tr>
<td><b>Definition:</b> Text here</td>
</tr>
</table>
<table cellpadding="4" cellspacing="0" style="border: 1px solid black;">
<tr class="row">
<td>
<table>
<tr>
<td><big>Key feature</big></td>
</tr>
</table>
</td>
</tr>
<tr>
<td>
<table>
<tr>
<td> </td>
<td><b>•</b> </td>
<td>Point</td>
</tr>
</table>
</td>
</tr>
</table>
<table>
<tr>
<td>
<table>
<tr>
<td><big>Associated feature</big></td>
</tr>
</table>
</td>
</tr>
<tr>
<td>
<table>
<tr>
<td> </td>
<td><b>•</b> </td>
<td>Point.</td>
</tr>
</table>
</td>
</tr>
</table>
<h4>INTRODUCTION</h4>
<p>Text here</p>
<h4>PROBLEM</h4>
<h4>INTRODUCTION</h4>
<p>Text is here</p>
<h4>EPIDEMIOLOGY AND PATHOGENESIS</h4>
<p>Text is here.</p>
<p>Text is here.</p>
<p>Text is here.</p>
<h4>OCULAR MANIFESTATIONS</h4>
<p>Text is here.</p>
<div>
<table>
<tr>
<td><img src="f045-7gr1.jpg" alt="#########"><br></td>
</tr>
<tr>
<td><img src="images/blank.gif" width="1" height="10" border="0" alt="#########"></td>
</tr>
<tr>
<td>
<p>Fig. 4-21 <span class="figure-caption"><b>Fig text</b>. Note blablabla.</span></p>
</td>
<td><img src="images/blank.gif" width="10" height="1" border="0" alt="#########"></td>
</tr>
</table>
</div>
<br>
<p>Text is here.</p>
<p>Text is here.</p>
<p>Text is here.</p>
<h4>DIAGNOSIS AND ANCILLARY TESTING</h4>
<p>Text is here.</p>
<div>
<table>
<tr>
<td><img src="f045-7gr2.jpg" alt="#########"><br></td>
</tr>
<tr>
<td><img src="images/blank.gif" width="1" height="10" border="0" alt="#########"></td>
</tr>
<tr>
<td>
<p>Fig. 4-21-2 <span class="figure-caption"><b>Fig text</b>. Add fig text </span></p>
</td>
<td><img src="images/blank.gif" width="10" height="1" border="0" alt="#########"></td>
</tr>
</table>
</div>
<br>
<h4>DIFFERENTIAL DIAGNOSIS</h4>
<p>Text is here.</p>
<h4>PATHOLOGY</h4>
<p>Text is here.</p>
<div>
<table>
<tr>
<td><img src="f045-7gr3.jpg" alt="#########"><br></td>
</tr>
<tr>
<td><img src="images/blank.gif" width="1" height="10" border="0" alt="#########"></td>
</tr>
<tr>
<td>
<p>Fig. 4-21 <span class="figure-caption"><b>Fig text. </b> (Fig text</span></p>
</td>
<td><img src="images/blank.gif" width="10" height="1" border="0" alt="#########"></td>
</tr>
</table>
</div>
<br>
<br>
<h4>TREATMENT</h4>
<p>Text is here.</p>
<h4>COURSE AND OUTCOME</h4>
<p>Text is here.</p>
<h4>CONGENITAL DYSTROPHY</h4>
<h4>INTRODUCTION</h4>
<p>Text is here.</p>
<h4>EPIDEMIOLOGY AND PATHOGENESIS</h4>
<p>Text is here.</p>
<p>Text is here.</p>
<h4>MANIFESTATIONS</h4>
<p>Text is here.</p>
<p>Text is here.</p>
<h4>DIAGNOSIS</h4>
<p>Text is here.</p>
<h4>DIFFERENTIAL DIAGNOSIS</h4>
<p>Text is here.</p>
<h4>PATHOLOGY</h4>
<p>Text is here.</p>
<h4>TREATMENT</h4>
<p>Text is here.</p>
<p>Text is here.</p>
<h4>COURSE AND OUTCOME</h4>
</body>
</html>