Made a mistake while filling online application

Once you have filled up an application form inserting a wrong information, the site may not open and this you are witnessing. In this connection, you have sent an email confessing your mistake. Now you have to write an application addressed to the chairman/ secretary whichever is applicable in this case indicating the details how such a lapse has originated. You indicate your application number and date along with your personal details so that your application can be tracked. Request the authority to offer you a chance to correct the mistake crept in the online format.
Send your application form attached with an acknowledgment letter to be affixed with the envelope containing your request. The acknowledgment receipt would reach to you once the application is received by the office. Preserve this receipt as a proof of your initiative.

This was a blunder on your part and if there are no editing facilities in the site then it becomes a problem as how to enter the site for applying or convince the authorities that it was done inadvertently. The only thing one can try is to send a personal application to the coordinator of the exam at the address provided in the site or send an email explaining the problem and asking to make change in the system by the system administrator so that you can apply as a fresh candidate. You say that they are not responding to your email so in that case send them a reminder and send a physical application also to their address. Keep a copy of the all of the correspondences with you so that if they ask you then you can produce it to show that you were active just after knowing your mistake.

If you were trying to apply in Himachal Pradesh public services then their contact information is -
Himachal Pradesh Public Service Commission, Nigam Vihar, Shimla, H.P. - 171002
E-mail: hppsc_shimla@msn.com
Enquiry ph. - 0177 - 2624313
Toll Free No. - 1800-180-8004
(Any working day between 10.00 AM to 05.00 PM)

If that does not help you can interact and communicate with some high officials there who are sometimes very helpful to the candidates and you must try this channel. Some of the officials and their contact numbers as given in the site are -
1. Shri Ajay Kumar, IFS (Retd.), Chairman, Ph: 2623793
2. Dr. Rachna Gupta (Former Editor, National Daily), Member, Ph: 2623796
3. Shri Ashutosh Garg, IAS, Secretary, Ph: 2623786
4. Ms. Ekta Kapta, HAS, Joint.Secretary, Ph: 2623857
5. Shri Rakesh Verma, Dy.Secretary, Ph: 2622015
6. Shri Yog Raj Sharma, Under Secretary, Ph: 2622015

Do not panic, while filling the form, sometimes some mistakes are made but there is a possibility of improvement in them. As you mentioned that once you have submitted the form, then you must have got a registration number on that email id which would have been included in your form. You must have received that email through a certain email ID which will not likely reply but will have some helpful links and mentions. Once you check that email carefully and looking at all those links, maybe you will get some suitable options from there.

You can also try and use this fixed no. to solve your problem by calling 1800-180-8004, this is the customer care contact number of the concerned body from where you will get complete information, after calling you will have to tell your registration number, which will be on your email id, the same number. After that, you will be told all the relevant information and after making necessary corrections in your form, it will be accepted.