There has been always a problem with anchor bookmarks in SharePoint 2010, the culprit is sp.core.js
file
It seems a duplicate of existing questions here:
Sharepoint 2010 and Anchor Tags
Do named anchors work in SP2010?
A little late to the party on this, but I just experienced this issue
myself and came up with a fairly effective solution.
As Lori said, it seems that SharePoint's built in JS can force scroll
issues that prevent anchors from working properly. The first issue you
might run into is the fixed-ribbon scrolling problem that has been
pretty well documented. Essentially the tag never scrolls, it's
the inner #s4-workspace tag that does all the scrolling. If you
need to fix this issue, I recommend Kyle Schaeffer's explanation.
Once you're past that, you may still have some issues. I was
experiencing the "jump" that you mention because pages were trying to
load at the anchor position, and then a SharePoint JS file was forcing
a scroll back to the top of the page. I eventually narrowed this down
to the sp.core.js script, which allows the following JavaScript code
to correct the problem:
function scrollToAnchors() {
if (window.location.hash != "") {
window.location.hash = window.location.hash;
}
}
ExecuteOrDelayUntilScriptLoaded(function () { scrollToAnchors(); }, "sp.core.js");
Hope this can help someone.