Some roads I edited no longer show up. What did I do wrong?

For example, I edited Mount Hamilton Road.
I tweaked a bunch of points so that it would match the GPS track better, split out the section I had GPS information on from the parts I did not alter, and removed the tiger:reviewed=no property from the section I tweaked.
The data for this road still shows up if I download the data to JOSM, but the segments of this road that I touched are missing from openstreetmap.org. Other roads I edited show up fine.
What determines when a road is displayed or not?

I did not see any means to revert my changes in the history, or anywhere else.

Mt Hamilton Rd. is back again.
I noticed that the “highway = secondary,tertiary” property was kind of weird, so I changed it to “highway = secondary” on all three segments. That seems to have fixed it.

Well, not quite fixed. The road shows up on Mapnik, but not osmarender
This link should show the relevant portion of the map:
http://www.openstreetmap.org/?minlon=-121.799530029297&minlat=37.376823425293&maxlon=-121.797561645508&maxlat=37.3780136108398

Zoom out a couple of times, then toggle between the two base layers to see part of Mt Hamilton Rd (CA 130) appearing and disappearing.

The Osmarender layer is not refreshed as often as the Mapnik layer. Plus the refreshment interval is “unpredictable”. The Mapnik layer is rendered on one centrally controlled server. The Osmarender layer is rendered decentralised by a multitude of volunteers. For more details see: http://wiki.openstreetmap.org/wiki/T@h

So if your fixes look good now on the mapnik layer, they will probably look good on the Osmarender layer tomorrow (or later).

It is now 48 hours since a section of Mt Hamilton Rd. dissapeared in osmarender. I went and did a manual render request for the two affected tiles in www.informationfreeway.org. Both tiles have been rendered now, and Mt Hamilton Rd. is still missing.

I’d really like some help to get that road to show up again.

Scratch the above. It appears that the web sites are a bit sloppy about how they cach things.
When I did ‘i’ to get information on the tile in question, it showed the correct render time, but the image of the tile it showed was an old cached version. a shift-reload got the new version with Mt Hamilton rd. visible.

But I can’t get the road to show up on www.informationfreeway.org. When I do a shift-reload, it zoom out to zoom level 1, zooming back in gets me back to the old cached image.

shift-reload on openstreetmap.org switcheds from osmrender back to mapnik, but switching back to osmrender, now shows Mt. Hamilton Rd. correctly.

I am very happy to see that I did not screw up the map.

I think you’ve found the answer: the old tiles were cached, which was why you were not seeing them refreshed with your changes. However, this caching behaviour is in the browser not on the server-side.

There is a useful layer available from the (+) tab on the RHS of the slippy map which allows you to browse the data in view. Click on data, and an overlay of actual OSM primitives appears. You can click on individual nodes/ways and view their tagging, who edited them and who last edited them. This is always worth doing if you think something may not have got up to the server, as the data layer makes direct API queries. There are a couple of quirks: its difficult (impossible?) to select ways within a bigger polygon due to a restriction in OpenLayers. For named highways this is rarely a problem as they can be identified in the left hand panel showing a list of objects.

HTH

It’s possible, but you need to manually restrict the area for the data layer to a rectangle within that bigger polygon.

I second the recommendation to use data layer for narrowing down possible causes for unexpected renderer behavior. Also, a forced refresh (shift-reload) in the browser is often a good idea when caching prevents updates.