i have cutom button in my Expence__c

in expense_c i have a field called as entity_name__c(lookup(Account))

so i have displaytype as  List Button

behavior as Display in existing window with sidebar

and i dont know what url should be placed  so want kind of url is to be palced 

your answer will be greatly appricatied

i want to integrate my website such that after my client  pass the payment gateway ,the account should be created in salesforce

please recommend me the best way for this

how can i use jsppage  in my iis server 

i have a pages created on asp but i need need to call few jsppage in that so how ca i do that