textbox validation for emptytext box?

Dear all ,

 

am working with asp.net jquery ajax,

 

now before execute jquery fuction i want to check the textbox was data or empty 

if it was empty i want to show alert and after focuse on the save textbox .

 

am trying to write out side of function writing a new validation for checking .but it waorks perfect .some time when i hit the cancle button insted of submite that time also it was chekcing and showing some error .so please suggest me to write the validations

in jqueary .simple required feild validaters..