Webb, who was only in the side due to an injury to Lionel Ainsworth, scored twice in three minutes in the first period to give Hereford a level of superiority which they rarely looked like losing.
Former Hereford striker Alan Connell tested Wayne Brown with a seventh minute header from Glenn Poole's free-kick.
And it was the Bees who looked the likelier side to open the scoring in the first 30 minutes.
Lee Thorpe had a header blocked on the line by Bulls skipper Karl Broadhurst in the 27th minute.
And then a minute later, Connell grazed the outside of a post with a 20-yard volley after Trent McClenahan's mis-directed clearance.
But on the half-hour, United took the lead when Webb blasted in from 15 yards after good set-up play from Clint Easton and Steve Guinan.
Then just three minutes later, Webb was on target again, cracking home from a similar position after Ben Smith crossed from the left of the area.
Hereford went on to dominate the remainder of the period and Easton twice almost added to the tally with long-range drives.
In the first minute of the second period, Webb went close to completing a hat-trick which he drove in from 20 yards only to see keeper Simon Brown fly through the air to pull off a stunning save.
Hereford went on to dominate possession, but it was Brentford who had the ball in the net next when Connell fired in only to see the strike ruled out for offside.
Smith fired narrowly wide after a neat interchange with Guinan on 73 minutes and the Bulls held on to the points without undue alarm.