Although PDF Plug-In for SimplyHTML reads any HTML it mainly focuses on transformation of HTML text documents with explicit formatting information rather than web pages.
Authors of web pages tend to omit formatting information in HTML code and rely on the default formatting of web browsers or other applications. The problem with this design is that there is no standardized way of formatting when no explicit formatting instructions are given. A page may appear differently when viewed in different applications.
Let's say a table is formatted with
<table><tr><td><p>Test text in cell 1</p></td></tr></table>
This HTML perfectly models a table structure (a table with one row and one column). However, it does not give information about the font family the text shall be displayed for instance.
A browser or other application may choose to display the text in Serif, another might choose SansSerif, so the actual appearance might look completely different. One can not predict how the appearance will look.
To make sure HTML is rendered in a comparable way over different applications formatting information should always be included explicitly.
<table style="width:80%"><tr><td><p style="font-family:Sans-Serif; font-size:12; font-weight:bold;">Test text in cell 1</p></td></tr></table>
Above HTML will ensure that the table width always is 80% of the width of display window and text will always be rendered in Sans-Serif, 12pt, bold.
It is a good idea to store formatting information along with the content of the document. The formatting information can be stored with each tag as in above example or it can be stored in a separate CSS style sheet the HTML file references. This way it is most likely that the document is rendered similarly over different applications.