Shahnawaz,
html:link is altogether different from html:submit, former is for referencing other links/resources from page and later is for submitting a html:form. html:link is get parsed or converted as <a href="".. />, ultimately..
Look what
Struts says about
html:link !
Now, though you can call an action using html:link, but this is not the true use of it, Why do you want a login page submitted by html:submit, really not a good practice.