open a link in another part of the page

[leo]

hey all,

1) i am new with dreamweaver and i dont know how to make a link open
an html file inside the same page.
for example i want a link located to a sidebar open a html file in the
main content of the same page and dont have to open a new tag or
window.

2) how can i make a button to go back to the main page??

thanks a lot