Values in session varaible

i have 2 pages page1.aspx having button1 
page2.aspx have 2 button back n submit when user click on back button it will go to page1.aspx 
den i want to save all values in text boxes save values in session varaible but its not working on page 1 submit

Session("UsrName") = wrd1.Text.Trim()
Session("UsrCompany") = wrd2.Text.Trim()
Session("UsrMobile") = wrd3.Text.Trim()
Session("UsrEmail") = wrd4.Text.Trim()
Session("Usrabout") = wrd5.Text.Trim()
Session("Usrdate") = wrd6.Text.Trim()
Session("UsrLngEvent") = wrd7.Text.Trim()
Session("UsrLocEvent") = wrd8.Text.Trim()
Session("UsrEventFor") = wrd9.Text.Trim()
Session("Usrbudget") = wrd10.Text.Trim()
Session("CategorySelect") = cblOptions.SelectedValue
den on page load of page 1
wrd1.Text = Session("UsrName")
wrd2.Text = Session("UsrCompany")
wrd3.Text = Session("UsrMobile")
wrd4.Text = Session("UsrEmail ...