[02/03] How to checkbox is empty

Hello friends..I have two textboxes on a form accepting url and submit button.when user clicks on submit button, it checks
1) whether the textboxes r empty
2) both textboxes must have same url
3) url must be between 2 to 25 chars..etc
if all these conditions r true then it redirects to another page..
I have taken server controls (textboxes and submit )..and try to write javascript on onclick of that button..but it gives error..like' ")" expected '. what is the easiest way to do that?

Use the built in validator controls. Use a regex validator to check if the URL is valid, and a compare validator to ensure both URL's are the same.