Links problems

Hey guys ,
I have a page index.html with 5 section one of them being contact , so the html is something like this :

now the above code is on my index.html .
now when i move to another page eg. backpage.html . on that page i have a link called contact us ,
i'd like that link to point back to the contact section in index.html ,
so i have the following code :
contact us
, now that does't work ,
any suggestions.