If you want to make money from your web site then you need to ensure you get lots of visitors. To get lots of visitors you should ensure the page is easy for search engines (google and yahoo) to spider.
Most search engines just spider the first 1000-5000 characters of the html making up a page.
Therefore, if your underlying code is full of rubbish, you will not be spidered efficiently and will get fewer visitors and will make less money.
For example, the following code
<B><FONT FACE="ARIAL" SIZE="3" COLOR="#000000">
<CENTER>
TECHNICAL REPORT AWARENESS INTERNET LINKS (TRAIL)<BR>
<FONT SIZE="1">A Defense Technical Information Center (DTIC)
Product</FONT>
<P>July 1, 2005<BR>
BIOTECHNOLOGIES<BR>
<FONT SIZE="2">Includes Human Factors Engineering (HFE) and
Human Systems Integration (HSI)</FONT></P>
</FONT>
Could just as easily have been written as
<H1>
TECHNICAL REPORT AWARENESS INTERNET LINKS (TRAIL)</h1>
<h2>A Defense Technical Information Center (DTIC) Product</h2>
<P>July 1, 2005<BR>
BIOTECHNOLOGIES<BR>
<div class ="text">Includes Human Factors Engineering (HFE)
and Human Systems Integration (HSI)</div></P>
The advantage of the second way of doing things is that search spiders understand the second example. The <H1> tag is an instruction to the spider that there is important information coming up.
In order to get the page to display correctly to human visitors we just need to add some rules for web browsers about how to display H1, H2, p, and 'text' elements.
This is best achieved with a separate css file which can apply to all pages on your site.
The result is less effort for you, more consistency across the site and better spidering leading to bigger profits all round.