Setting specific FPS for video I have a video that was recorded using my laptops webcam. 

According to the mplayer tool, my FPS for this video is set to 29.75 FPS (using the mplayer -identify -frames 0 myfile.webm command).

In blender's video sequence editor, under Dimensions, FPS, I choose custom, and then type in 29.75 for my video, but when I press enter, it rounds up to 30FPS. My video and audio tracks don't line up.

Why doesn't it let me set the specific FPS? How can I best rectify this situation?

Thanks.
As you have noticed the FPS can only be set to integer values. To get a fractional frame rate you need to also set the framerate base which you can find right under the FPS.

The easy way to get the right base value is to enter a calculation which is the set fps divided by the target rate. eg 30 / 29.75, when you then press enter it will show the value of 1.008 and the frame rate will show as Custom (29.75 fps)