The Irrelevance of Resolution on the Web:
Right.. The technical explanation...
Resolution generally refers to the conversion between on-screen pixels and on-paper dots of ink. The resolution (dpi) of an image file is an extra piece of information that is only read by printers (and occasionally things like photoshop for doing print previews).
72 dpi is often used as a default setting when working with on-screen images, but only because photoshop demands that you put something in the resolution box. 72 dpi is derived from the very old and now obsolete 'standard' cathode ray tubes made in the 70's (tv-style monitors). In the modern day, the actual resolution of monitors ranges from 72 dpi (old monitors and people with poor eyesight who set monitors display larger to make them easier to read) right up to around 250 dpi (huge, professional high-def LCDs). None of which actually matters.
Web browsers don't even bother to read the resolution data attached to an image. One pixel in the image file is translated to one pixel on the user's computer screen. If a user has a monitor of 800 x 600 pixels (currently the most common) then an image that is sized to 800 x 600 pixels will fill their screen, regardless of the image's DPI.
Weblobe actually takes care of image resizing for you. You feed it a single master file and it makes all the required thumbnails, inline and full-page versions for you, all scaled according to the constraints of the design and layout of your website. Weblobe's image manager, like web browsers, doesn't care about what you put in the resolution box in photoshop, it's only concern is with the number of actual pixels in the file.
The Exception to the Rule:
If you want people to be able to download a very large version of an image that they can print for themselves it's a good idea to set the resolution to somewhere between 200 and 300 dpi.