Outlook web Access can utilize HTML formatting with the use of signatures.
There are a few restrictions to the use of complex formatting.
You can not use a product like Microsoft Word to create a complex signature that contains tables.
Doing so can break the web based options page.
Should you encounter a pop up error warning using Internet Explorer from a corrupted signature,
You will need to use Outlook Web Access Light (option at log in screen) to clear the bad signature.
Once in the light mode, you can choose in options to replace the current signature.
Simply save the new signature, log out and back in under the normal mode.
You can now use the built in editor to format your signature as you like.