What does 3D mean in this html email?

I’m trying to understand source code from an html email from someone else did. What does 3D mean? I see it’s in the meta data and used throughout.

I’ve included a snippet of the top portion of the code below. Sorry I don’t know how to indicate this is code here.

Thank you,

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.=
<html xmlns=3D"http://www.w3.org/1999/xhtml">
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DUTF-8" />
<title>title here</title>

<table width=3D"650" border=3D"1" cellpadding=3D"0" cellspacing=3D"0" align=
<tr> <td>

<table width=3D"650" border=3D"0" cellpadding=3D"0" cellspacing=3D"0" align=
<td colspan=3D"3">
<a href=3D"http://e.ccialerts.com/a/hBNCRBwB8N6AvB8WQuONhRMu1Sp/cnyb8a"><im=
g src=3D"http://f.chtah.com/i/10/2084020271/12.15.10_book_header.gif" width=
=3D"650" height=3D"300" alt=3D"Subscribe to Business for=
=03 only $29.95 and get the Lists=03with your paid subscript=
ion! " border=3D"0"></a></td>

The HTML is encoded with what is called quoted-printable. Basically an = at the end of a line indicates a line wrap, so


should be read as “hello” and not as “he llo”

because the = has this special meaning some other character (sequence) is needed to put = characters in the text literally, and that is =3D