Hi there, Yes you can. But you need to use FCK editor or similar. Use the view source button, and paste the HTML code.
@ Zafar FCK Editor is an WYSIWIG editor with some great features and the only one for Joomla that I know that doesn't alter HTML code if its pasted into the content field. @Fortify JoomlaFCK is installed as a Mambot, now know as a Plugin. To use a Plugin you need to set it to "Publish" in your Administrator Panel under Site Mambots There is more info about the Plugin on the joomla extensions page JoomlaFCK
You don't need an editor to show a html code in the content. If you have any further problems I would suggest posting in joomla forums.
You can go to "Global Configuration" and where it gives you an option "Default WYSIWYG Editor:" select "no WYSIWYG Editor", then you can enter your html code
You can use mod_html to paste html directly to joomla. Mod_html allows you to Add Any HTML or JavaScript code to your Mambo or Joomla Website. I used this module to insert the google analytics script into every page of my website, and it worked perfectly.