invisable feet not working all shoes look like I am wearing double feet, can someone help me

[Wiggles007 Tamale]

Invisable feet not working  all shoes appear to me as thought I am wearing double feet.  boots look ok but no shoes appear properly.  any ideas waht is wrong?

[KarenMichelle Lane]

For a while now shoe merchants have been including a matching alpha texture to erase the pesky LL foot deformer. You must use the alpha texture that came with your purchased shoes. If you have older shoes [pre alpha texture] go online to the Market Place and obtain the demo version of the shoe line you're having issues with. Grab the alpha foot texture out of that package and place it in the package for your problematic shoes. Repeat with each merchant shoe line until all shoes with this issue are corrected.

You can also visit your shoe merchants in-world as well, but be sure to leave your lindens at home

[Lindal Kidd]

To expand a bit on KarenMichelle's answer...

Older shoes use a specially scripted prim called an "invisiprim" to hide the avatar feet, where they would show under the sole of a high heeled shoe.  The invisiprim makes use of a loophole in the SL rendering system to work its magic.

When LL implemented Mesh and shadows, this loophole got closed.  Now, invisiprims will not work for anyone who has a mesh-enabled viewer AND has shadows enabled.

Newer shoes use a different method, an alpha texture, to hide the avatar foot.  There are free alpha foot masks out there; pick some up, and try them until you find one that works for a particular pair of shoes without erasing too much of your ankles or calves.

[KarenMichelle Lane]

Ohhhhh - High Five - Good follow-up

[Lucretia Brandenburg]

There seems to be some sort of glitch in recent weeks with alpha layers for feet. Why it's just those alpha layers, I don't know, I do know that I put on alphas for several different body parts and feet were the only one with problems. The alpha mask doesn't show up and the avatar's feet show through. I and a few other people I know who wear mesh feet were having this problem. Removing all clothing layers, clearing cache and relogging helped.