you can translate the nucleotide sequence using Expasy translate tool http://web.expasy.org/translate/. This will provide you all possible frames of which most accurate one can be identified by comparing the size of protein.

First of all be sure that what you want to identify either intron or exons with in the nucleotide sequence, your query says that you want to determine the open reading frames of gene. as i understand that you have large nucleotide sequence with you and you want to identify the exons from that or you can say protein coding sequence, for that you can simply use the Augustus web interface server for gene prediction http://bioinf.uni-greifswald.de/augustus/submission.php.

or you can simply use the NCBI ORF finder http://www.ncbi.nlm.nih.gov/gorf/orfig.cgi.

Sir, I want to know if any online tool can predict the specific position of an intron in a nucleotide sequence

if you know your exon region (ORF), you will be able to detect your introns from their respective splicing site. There are plenty of software to detect the splicing site.

 Thank you sir for the suggestion. It is of great help.

Dear Pragya,

If you convert the sequence file to BEd file format. Pavis online software will

http://manticore.niehs.nih.gov/pavis2/

https://www.youtube.com/watch?v=0EP5wQ0pyvU

This question was asked before on researchgate see the link below

https://www.researchgate.net/post/How_can_I_identify_introns_and_exons_in_a_gene_sequence_ORF

Good luck

the intron starts and ends with specific sequences (like AG ), from that there are software which predict the intron in the gene sequence

http://www.cbs.dtu.dk/services/NetGene2/