You can Add a PageManager control to the page. Then use these properties to establish focus, see the following attributes
1. FocusOnChange - Set the focus to the field after a change is made when there is a validation error. When true, focus is set on the field.
2. FocusOnSubmit – Set focus to the first field that generates a validation error when the page is submitted. When true, focus is set on the field.
3. FocusAfterAlert – Set focus to a field with an error after the alert is displayed when using the ErrorFormatters that display alerts. Supported by "Image with Alert" (AlertImageErrorFormatter) and "HyperLink with Alert" (HyperLinkErrorFormatter). When true, focus is set to the field after the alert is dismissed.
for more detail switch to following link
http://learningdes.peterblum.com/Validation/Validators/GettingAttention/Focus.aspx
Thanks
Koolprasd2003
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]