I would like a review what is wrong with my code?

can someone edit my code...
the tag <sup> make me extra space ...
html code

<p class="mainText">

And this is the text <span style="font: bold 12px arial; color: #000;">
And this is the text</span> software that<br/>
And this is the text And this is the text And this is the text. 
And this isl<br/>
And this is the textAnd this is the textAnd this is the text <br/>
<span style=" font:bold 11px Arial; color: #000;line-height:5px; ">
And this is the text. And this is the text 15
<sup><span style=" font: 11px Arial; color: #000;line-height:5px; ">
avi</span></sup>
And this is the text</span><br/>
And this is the text And this is the text.
				
</p><br/>

Code (markup):

css code

.mainText{

	position: relative;

	font: normal 11px arial;

	top: 85px;

	left: 30px;

	width: 570px;

	height: auto;

	color: #000000;

	border: solid 0px BLACK;

}

Code (markup):

the relevant page -
http ://www.coarch.co.il/123/raw/advantage.html

 

Been so long since I've done this so I am not sure of this is the best way. I don't use <sup> though, I use a <span> with a class, e.g. "superscript" with the following CSS:

.superscript { font-size: 0.6em; position:relative; top: -0.6em; }

Code (markup):

EDIT: I experimented a little and this solution is better in my opinion:

sup { vertical-align: baseline; font-size: 0.6em; position:relative; top: -0.6em;  }

Code (markup):

That way, you can still use <sup> and not worry about classes.

There is probably still a better solution though, I don't like this one as x² is read by search engines and other parsers as "x2" instead of x^2... maybe a hidden span in between, e.g.:

<p>66% of statistics are made up on the spot<span class="hidden">, see footnote #</span>¹</p>
<h2>Footnotes</h2>
<p>1: your mum</p>

Or is that just overkill?

 

EDIT: I experimented a little and this solution is better in my opinion:

sup { vertical-align: baseline; font-size: 0.6em; position:relative; top: -0.6em;  }

Code (markup):

how can i still use <sup> and not worry about classes.