Deleting pseudo-duplicates...

[Vicente Lopez]

Hello,

I have a table with this values:

id    value    time
1        12    200704042112
2        12    200704042120
3        14    200704042125
4        14    200704042131
5        17    200704042140
6        14    200704042143
7        20    200704042145
8        20    200704042148


I want to delete the rows with the same value of the preceding one, the 
spected result
looks like this:

id    value    time
1       12        200704042112
3       14        200704042125
5       17        200704042140
6       14        200704042143
7       20        200704042145


but I don't have any idea how make this select...