i develop a software in PHP . but when i press back button which is located at the left top of browser. then there is error. infact it is not coding error. it is such type of error like (document expired) so after that when i refresh the page, then it show the data. so plz guide me

If you click on one of the topics in this forum and start to type a response, and then try to navigate away from the page using the browser's back button, a javascript alert pops up verifying that you want to leave the page or stay on the page. Maybe post in the javascript forum asking how this function is acheived.