In my outlook when i check my new emails after that it delete them from my web email ???

If you do not want Outlook to delete your emails and you want them to still be accessible in your webmail, do this: Go to Tools, Email Accounts, view or change existing email accounts, hit next, now choose the email account that you do not want Outlook to delete the emails from, highlight it and click change. Then in the lower right hand corner click More Settings. Now click the advanced tab and at the bottom there is a box to check to tell Outlook to leave a copy of the message on the server. Thus when you check your email with Outlook, it only downloads a copy and does not remove it from your webmail. If you want the email deleted you will have to do it through webmail or tell it not to leave a copy on the server. Hope this helps! This instructions are for Microsoft Office Outlook 2003.

In my outlook when i check my new emails after that it delete them from my web email ???
May be you have set the View for "unread mails" only. After reading, the mail vanishes from the view as it is already read. Set the view to "all mails" to see all