Make Log ERROR FILE in vb.net

Dim FILENAME As String = Server.MapPath("style\style.css")
Dim srw As StreamWriter = New StreamWriter(FILENAME)
srw.WriteLine(".subCategories{")
srw.WriteLine("font-family:" & var152 & ";")
srw.WriteLine("font-size:" & var1 & "px;")
srw.WriteLine("border-bottom-width:" & var3 & "px;")
srw.WriteLine("border-bottom:" & var4 & ";")
srw.WriteLine("border-bottom-color:#" & var5 & ";")
srw.WriteLine("}")