A Hyperlink Control 
displays text as a hyperlink by wrapping it in <a></a> tags. It can
- run a server-side script by attaching scripts to the On Click event property
- navigate using a URL by setting Link is external and providing an External URL and optionally a target.
When running a server-side On Click event, clicking a hyperlink will also perform validation on any Field Controls preceeding it and submit any modified field values to the server. The Skip Validation property instructs the hyperlink to skip the validation process before submitting the field values to the server.
You can set a hyperlink's text by double clicking it and set the title attribute of the link by setting the Mouse over text property.