A  signature can appear automatically at the bottom of an email or a post to a forum. 
Each email provider and bulletin board has a different way to set it up.  Many email sites have it under Options. 
(Yahoo choose Color and Graphics first and then HTML)
Most signatures contain one or more of the following:

bulletyour name
bulletyour email address
bulletsnail mail address and phone
bulletyour web site address
bulleta graphic.

The graphic requires that you put in the follow HTML code <img src="url-of-graphic">.  Be sure to insert the complete URL of the graphic such as http://sumware.com/UCC/images/sebasti.gif between the two quote-marks "
for . (see below for procedure to copy the URL)

the HTML <img src="http://facultu.ucc.edu/business-greenbaum/images/faces.gif"> points to a the graphic

It must be entered EXACTLY as above:

bullet < (less than) before everything
bullet > (greater than) at the very end
bullet img src with a space in-between img and src (that is the only space between the < and the >.) 
bullettwo double quotes "
bulletbefore the http
bulletbefore the >

The best way to get the web address of of graphic is to

bulletright click on it
bulletselect Properties
bullethighlight the complete URL
bulletcopy the ENTIRE address to the clipboard
bulletpaste it between to "s.

Step by step

  1. go to window with the web page that has the graphic you wish to use
  2. right click on the graphics (be sure that you have permission to use that graphic)
  3. select Properties from the short menu
  4. highlight the URL (everything from http:// to gif or jpg)
  5. point at the highlighted letters
  6. right click
  7. select copy from the short menu
  8. go to the window where you are creating your signature
  9. type <img src="">  Note there are two double quotes
  10. click between the two " (quotes)
  11. paste (Ctrl+V or right click Paste) this name that is on the clipboard from step 7 between the two "

Prof. Maureen <img src="http://sumware.com/UCC/images/sebasti.gif">

cart23.gif body15.gif

artist0b.gif mickey2.gif [pothead-0003.gif] Man_Frowning_at_Computer.jpg
r-horse-a.gif Talking_on_Phone.jpg
garfield2.gif cart7.gif From Art by Cheryl lug2m.gif - 1.8 K Briefcase_1.jpg
      happy face Confused Emoticon

cart10.gif bugs2.gif   car plane4-a.gif Praying_at_Computer.jpg
chess6-a.gif hand plane7-a.gif Happy_Computer_Man.jpg
chess13.gif Icon Preview flower pot apple From Art By Cheryl Fish_-_Cartoon_26.jpg
boy6.gif cart22.gif earth6.gif coffe [pothead-0019.gif] Fish_-_Cartoon_03.jpg
football-a.gif clock1-a.gif From Art By Cheryle tnt-a.gif From Art by Cheryl
soda Drinking_Water.jpg push pin pencil Fish_-_Cartoon_07.jpg Fish_-_Cartoon_21.jpg Fish_-_Cartoon_22.jpg

Using something special:

Find a graphic one you like  that is small (less than 2k).  If you find one at a free clipart site, it is courtesy to store it on your own page if you intend to use it as a signature.  To do that you:

bulletpoint at it
bulletright click
bulletselect Save Picture As
bulletselect a drive (M at school or C: at home and a directory)
bulletmodify the name if you want
bulletgo to Tripod (or some other place in cyberspace where you have space) and Upload it
bulletput its URL between the "" .
For example <img src="http://yoursite/images/yourpicture.jpg">
Note:  Rather than type that, 
bulletpoint at the picture
bulletselect Properties, 
bullethighlight the URL (everything from http:// to gif or jpg)
bulletpoint at the highlighted letters
bulletright click
bulletcopy