Hi Raga,
There's been a lot of questions asked about this on the forum, just search for "Webservice and trigger" or "web service". Most of these posting threads should end with the observation that its not a good idea to call a webservice directly from a trigger
(it makes your database insert process not only slow but fragile), but instead use service broker as a level of indirection (i.e. trigger writes service broker message, service broker activation program calls webservice).
Hope this helps, Cheers, Bob