I always add my extra html markup to the description field. First, I'll explain the hyperlink, which I think is the most important since you can provide your own site with some nice inbound links this way.
here's an example of the syntax for a basic hyperlink for a listing:
<a href="http://www.remericasomersetrealty.com/listings/lakeproperties.html">
South Central Michigan Lake Homes and Properties
</a>
note that that actual web page is specified, but the text that will show up as hyperlinked on the rendered craigslist or backpage webpage is South Central Michigan Lake Homes and Properties
For more on the correct syntax for hyperlinks see http://www.w3schools.com/html/html_links.asp
Here are some more simple examples of html tags for basic formatting,
to display this - type this
--------------------------
This is bold - <span style="font-weight: bold;">This is bold</span>
italic - <span style="font-style: italic;">italic</i>
carriage return- <br>
Other examples of values of the style attribute for a span tag that you may want to read up on are:
color: blue;
font-size: medium;
Here's a larger example of what you can do.
It's some html that I inserted into a recent craigslist add. Note that some of these tags are deprecated, meaning that they may be obsolete in future versions of html, and you'll want to look into specifying them as style attribute values of span or div tags in the future. I'll leave that lesson out here for simplicity.
<b>
<font size="+1">
Remerica Somerset Realty
</font>
</b>
<br>
Somerset, MI 49281<br>
517-547-6525<br>
<img id="plain" src="http://www.remericasomersetrealty.com/rsr-email.bmp">
<br>
<table>
<tr bgcolor="#F0F5FF">
<td>
<a href="http://www.remericasomersetrealty.com/listings/277.html" title="Click here for Details on 11125 Waldron Rd, Jerome, Michigan 49249">
<img src="http://www.remericasomersetrealty.com/images/listings/thmb_11125__Waldron_Rd-Jerome-MI-49249-437.jpg" width=150 alt="11125 Waldron Rd, Jerome, Michigan 49249" >
</a></td>
<td>
<a href="http://www.remericasomersetrealty.com/listings/277.html" title="Click here for Details on 11125 Waldron Rd, Jerome, Michigan 49249">
CRYSTAL LAKE, MI LAKEFRONT WITH LAKE LEANN, MI ACCESS</a><br><font size="-2">THIS DISTINCTIVE CUSTOM DESIGNED HOME OFFERS A MEDITERRANEAN CONTEMPORARY STYLE HOME COMPLETE WITH A GATED COURT YARD TO THE ENTRANCE AND A PORTICO DE.....</font></td>
<td align="right">$669,000</td>
<td align="right">5,566</td>
<td align="right">5.08</td>
<td>Hillsdale</td>
</tr>
<tr bgcolor="#FFF5F0">
<td>
<a href="http://www.remericasomersetrealty.com/listings/230.html" title="Click here for Details on 10500 Somerset Rd, Somerset, Michigan 49281">
<img src="http://www.remericasomersetrealty.com/images/listings/thmb_10500_Somerset_Rd-Somerset -MI-49281-138.jpg" width=150 alt="10500 Somerset Rd, Somerset, Michigan 49281" >
</a></td>
<td>
<a href="http://www.remericasomersetrealty.com/listings/230.html" title="Click here for Details on 10500 Somerset Rd, Somerset, Michigan 49281">
LAKEFRONT HOME 50 MINUTES FROM ANN ARBOR, MICHIGAN</a><br><font size="-2">THIS SPECTACULAR WATER FRONT HOME IS SECLUDED FROM THE ROAD BY A RIDGE OF PINE TREES AND HAS STUNNING VIEWS LOOKING OUT TO THE MAIN LAKE FROM A QUIET .....</font></td>
<td align="right">$288,000</td>
<td align="right">2,424</td>
<td align="right">0.19</td>
<td>Hillsdale</td>
</tr>
<tr bgcolor="#F0F5FF">
<td>
<a href="http://www.remericasomersetrealty.com/listings/252.html" title="Click here for Details on 10650 Glendalough Ln, Somerset, Michigan 49281">
<img src="http://www.remericasomersetrealty.com/images/listings/thmb_10650_Glendalough-Somerset-MI-49281-259.jpg" width=150 alt="10650 Glendalough Ln, Somerset, Michigan 49281" >
</a></td>
<td>
<a href="http://www.remericasomersetrealty.com/listings/252.html" title="Click here for Details on 10650 Glendalough Ln, Somerset, Michigan 49281">
WATER FRONT HOME FOR SALE 50 MINUTES WEST OF ANN ARBOR, MI</a><br><font size="-2">EXCEPTIONAL 1.29 ACRE YARD WITH 62 FEET OF SANDY BEACH ON THE LAKE IN A QUIET BAY WITH MAIN LAKE VIEWS. MATURE AND TREE SHADED YARD WITH SCREENED GAZ.....</font></td>
<td align="right">$254,000</td>
<td align="right">2,080</td>
<td align="right">1.29</td>
<td>Hillsdale</td>
</tr>
<tr bgcolor="#FFF5F0">
<td>
<a href="http://www.remericasomersetrealty.com/listings/241.html" title="Click here for Details on 10770 Arrowhead Circle, Jerome, Michigan 49249">
<img src="http://www.remericasomersetrealty.com/images/listings/thmb_10770_Arrowhead_Circle-Jerome-MI-49249-345.jpg" width=150 alt="10770 Arrowhead Circle, Jerome, Michigan 49249" >
</a></td>
<td>
<a href="http://www.remericasomersetrealty.com/listings/241.html" title="Click here for Details on 10770 Arrowhead Circle, Jerome, Michigan 49249">
WATER FRONT HOUSE FOR SALE IN SOMERSET CENTER, MICHIGAN</a><br><font size="-2">SPECTACULAR VIEWS. RANCH STYLE HOME WITH FULLY FINISHED WALKOUT AND FRONTAGE ON PRIVATE ALL SPORTS SOUTH LAKE LEANN. DOCK YOUR BOAT AND ENJOY THE FA.....</font></td>
<td align="right">$199,000</td>
<td align="right">2,240</td>
<td align="right">0.26</td>
<td>Hillsdale</td>
</tr>
<tr bgcolor="#F0F5FF">
<td>
<a href="http://www.remericasomersetrealty.com/listings/181.html" title="Click here for Details on 14175 Tralee Dr, Somerset, Michigan 49233">
<img src="http://www.remericasomersetrealty.com/images/listings/thmb_14175_Tralee_Dr-Somerset-MI-49233-153.jpg" width=150 alt="14175 Tralee Dr, Somerset, Michigan 49233" >
</a></td>
<td>
<a href="http://www.remericasomersetrealty.com/listings/181.html" title="Click here for Details on 14175 Tralee Dr, Somerset, Michigan 49233">
LAKE ACCESS HOME NEAR PARK, 20 MINUTES SOUTH OF JACKSON</a><br><font size="-2">THIS SUPERB HOUSE IS BUILT INTO THE SIDE OF A SMALL HILL AND REACHES SKYWARD WITH A TWO STORY ENTRANCE AND FOYER. NEAR MAIN PARK AND HAS OUTSTANDING V.....</font></td>
<td align="right">$164,000</td>
<td align="right">2,003</td>
<td align="right">0.34</td>
<td>Hillsdale</td>
</tr>
</table>
The rendered ad then looks something like this:
Remerica Somerset Realty
Somerset, MI 49281
517-547-6525
CRYSTAL LAKE, MI LAKEFRONT WITH LAKE LEANN, MI ACCESS THIS DISTINCTIVE CUSTOM DESIGNED HOME OFFERS A MEDITERRANEAN CONTEMPORARY STYLE HOME COMPLETE WITH A GATED COURT YARD TO THE ENTRANCE AND A PORTICO DE..... | $669,000 | 5,566 | 5.08 | Hillsdale | |
LAKEFRONT HOME 50 MINUTES FROM ANN ARBOR, MICHIGAN THIS SPECTACULAR WATER FRONT HOME IS SECLUDED FROM THE ROAD BY A RIDGE OF PINE TREES AND HAS STUNNING VIEWS LOOKING OUT TO THE MAIN LAKE FROM A QUIET ..... | $288,000 | 2,424 | 0.19 | Hillsdale | |
WATER FRONT HOME FOR SALE 50 MINUTES WEST OF ANN ARBOR, MI EXCEPTIONAL 1.29 ACRE YARD WITH 62 FEET OF SANDY BEACH ON THE LAKE IN A QUIET BAY WITH MAIN LAKE VIEWS. MATURE AND TREE SHADED YARD WITH SCREENED GAZ..... | $254,000 | 2,080 | 1.29 | Hillsdale | |
WATER FRONT HOUSE FOR SALE IN SOMERSET CENTER, MICHIGAN SPECTACULAR VIEWS. RANCH STYLE HOME WITH FULLY FINISHED WALKOUT AND FRONTAGE ON PRIVATE ALL SPORTS SOUTH LAKE LEANN. DOCK YOUR BOAT AND ENJOY THE FA..... | $199,000 | 2,240 | 0.26 | Hillsdale | |
LAKE ACCESS HOME NEAR PARK, 20 MINUTES SOUTH OF JACKSON THIS SUPERB HOUSE IS BUILT INTO THE SIDE OF A SMALL HILL AND REACHES SKYWARD WITH A TWO STORY ENTRANCE AND FOYER. NEAR MAIN PARK AND HAS OUTSTANDING V..... | $164,000 | 2,003 | 0.34 | Hillsdale |
Click Here to see this ad in it's natural habitat, but keep in mind that the ad expires in 45 days.