some questions about forms submit

Hi,
There is Form on my webpage. I want users to input any chars-even html tags- in this form and after they submit , the user input save to DB.
I have some question:
1- If use ValidateRequest="false" decrese webApplication security?
2- If I don't use  ValidateRequest="false" then If I enter chars like ?><>? I encounter this error
A potentially dangerous Request.Form value was detected from the client (ctl00$MainContent$com_email="M<SC?XMC?<>XZc").
How Could I set ValidateRequest="True" and not see above error while submit html tags to form?
 
Regards
 

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