A parse error is when you make so blatant a mistake (usually a very simple one) that the validator doesn't know how to interpret the code that comes after it. In this case, it's the linebreak between those two lines. You presumably mean to say ".indexlist p {" (referring to all <p> elements in .indexlist). HTML (and XHTML - good work!
) doesn't mind linebreaks; CSS does.
Code:
<p class="indexlist">
This doesn't do anything. The paragraph is already styled by the class of the div; classing it doesn't make any difference - or wouldn't do, if not for:
Code:
.indexlist { float: right;}
.mainmenu { display: block;}
Why don't you put this in the stylesheet?
As for learning to write nice code... I suggest the validator
Try to get it to validate as the strictest doctype you can find (XHTML1.1 Strict). Couple of days wrestling with that and I... well... I gave up and reverted to XHTML1.0 Strict. But at least I tend to write that from scratch nowadays 
(shudder) Imagemaps with XHTML1.1. It kept telling me I couldn't have a "#" in the usemap attribute. Of course, without it, nothing worked. All nice and valid, though.
I did this:
HTML Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Lira Art Gallery - Showcasing original artists of all mediums</title>
<meta name="description" content="Our online art gallery showcases original artists of all mediums including photography, poetry and painting."/>
<meta name="keyword" content="art, painting, photography, online art, gallery, artists, web design, poetry, original artwork, professional, purchase art"/>
<meta http-equiv="imagetoolbar" content="no"/>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<link type="text/css" rel="stylesheet" href="lira_files/lira.css"/>
<style type="text/css">
/*<![CDATA[*/
.indexlist { float: left;
text-align: center;
margin: 0;
padding-left: 1%;
padding-right: 1%;
}
.mainmenu { display: block;
margin: 0pt;
padding-left: 1%;
padding-right: 5%;
height:100%;
float: left;
}
/*]]>*/
</style></head>
<body>
<div style="text-align:center;">
<img src="lira_files/Liragallerygif.gif" alt="Welcome to Lira" style="border-style:none;" height="49" width="402"/>
<h3>Welcome to Lira</h3>
<h4>An online gallery showcasing artists of all genres and mediums</h4>
<div class="mainmenu" style=""><a href="http://www.lira.ca/artists.htm"><img src="lira_files/Artistsgif.gif" alt="Artists" style="border-style:none;" height="15" width="52"/></a><br/>
<br/>
<a href="http://www.lira.ca/galleries.htm"><img src="lira_files/Galleriesgif.gif" alt="Galleries" style="border-style:none;" height="15" width="64"/></a><br/>
<br/>
<a href="http://www.lira.ca/submissionsandinquiries.htm"><img src="lira_files/Submissionsinquiriesgif.gif" alt="Submissions & Inquiries" style="border-style:none;" height="37" width="88"/></a><br/>
<br/>
<a href="http://www.lira.ca/salesshipping.htm"><img src="lira_files/Salesshippingpoliciesgif.gif" alt=" Sales & Shipping" style="border-style:none;" height="37" width="66"/></a><br/>
<br/>
</div>
<a href="http://www.lira.ca/webdesign.htm"><img src="lira_files/Webdesigngif.gif" alt="Web Design" style="border-style:none;" height="19" width="88"/></a></div>
<div class="indexlist" style="width: 70%;">
<p class="mainmenu" style="text-align:center;">Artistry comes in many forms and
spans eras, genres and cultural boundaries. It is a Muse to which
person can relate, no matter what their taste, and the constant
evolution and revolution of our world provides canvas and palettes for
all varieties of artists.<br/>
The photographer who sees the world in shades of light filtered through their eyes and into ours.<br/>
<br/>
The artist who draws, paints and sculpts our imaginations with their own.<br/>
<br/>
The writer whose words provide not only inspiration, but also offer a
deeper sense of meaning whether we are living day to day or are seeking
the divine.<br/>
<br/>
The digital muse who creates our electronic world with not only a
smoothly designed, easy-to-use medium but also textures beauty with
functionality.<br/>
<br/></p>
</div>
</body></html>
It wasn't valid, I had to validate it! Stepped it up to Strict, too.
It needs to be tweaked.
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