When Mark Darcy goes to pick up Bridget's diary from the table (just after Bridget goes off to her bedroom to change into her 'genuinely tiny knickers'), the diary is on the 29th November. The next shot, of him actually picking up the book, shows it to be open on the 10th/11th November.
While in the restaurant with friends, a brand new cell phone comes out of its cellophane bag twice. The first time, the bag is held upside down and the phone slides out into a waiting hand, immediately after, it is pulled out of the bag.
When Mark leans in to kiss Bridget outside her door (as Shazzer, Jude and Tom look on from the car), Mark's head is tilted to his right in shots of Bridget and to his left in shots of him so that neither character is obscured by the others' head.
When we first see Bridget writing in her diary, listing the type of person she's not going to get involved with (with narration), she is writing on the left-hand page. In the next shot, she is at the bottom of the right-hand page.
In the scene in which Bridget's Mum talks to Bridget about leaving her Dad, Julian appears and hovers in the background in one shot, and is gone in the next but reappears and repeats his actions from the earlier shot.
At the married couple's dinner party, the level of wine in Bridget's glass changes. When she first picks it up it is half full, in the next shot it is full and in the next shot, it is half full again (without her having time to have consumed that much).
When they are in the lake, and Daniel is about to fall down, the overtaking gets close to Bridget and she is combed, when you go away his uncombed hair is seen, you approach and again he right now is combed with the totally straight hair.