In your trigger "Trigger1" the script line

set @id1=(select id from sal_t)

result in more than one row when you are inserting the second row to the "sal_t" table
So it result in the error "Subquery returnes more than 1 value.This is not permitted when the subquerry follows=,!=,<,..... or when the subquery is user as an expression."

Alter the trigger as follows,

alter TRIGGER Trigger1
ON dbo.sal_t
declare @id1 int
set @id1=(select top 1 id from sal_t)
insert into emp_t values(@id1,'ram')

It solves your problem. But the Trigger is not meaningfull. Can you please tell me the purpose of the trigger so that I can give you the response. Do you want to insert the last inserted id to emp_t table with the name as ram?