HOLLYWOOD — The nets have trotted out their fall skeds for advertisers, but they’re hardly etched it stone.

With the ratings races tighter than ever, and each network looking to give its new shows their best chance to shine, we may see some sked-shifting in the next few weeks.

Under particular scrutiny are hours loaded with dramas like Wednesday at 9 (including ABC’s “Lost” and NBC’s promising new “E-Ring”) and Thursday at 8 (with “Alias” and “Smallville” moving in).

Here are some early thoughts on the fall skeds:

  • NBC must not have thought much of its comedy development or it would have gone with a four-pack on Tuesday and shaken the cobwebs out of its tired Thursday twosome of “Joey” and “Will & Grace.”

Outside of maybe Saturday, Tuesday from 8 to 9 in the fall (before “American Idol”) is the only logical place for the Peacock to give new laffers a shot.

  • With CBS and Fox shifting from comedy to drama, all six broadcast nets will air dramas in Wednesday’s middle hour. ABC’s “Lost” is at the head of the class, meaning newbies “Criminal Minds” on CBS and “E-Ring” on NBC will battle it out for second.

NBC has probably looked at moving its high-profile “E-Ring” out of the slot, but this remains the best spot for it, and it figures to get the strongest lead-in (from the Martha Stewart “Apprentice”). But how about a name change?

Most likely shift would come at Fox, where “Head Cases” might best be replaced by a reality skein like “Trading Spouses” or “Nanny 911.”

  • While there’s a drama glut on Wednesday, there’s also a rare sitcom surplus on the night. Of the 27 comedies the Big Four have skedded for fall, six of them (two apiece on ABC, CBS and Fox) air in the night’s opening hour.

CBS seems to be the odd net out at 8 with “Still Standing” and “Yes, Dear.” But since there’s no other logical slot on the Eye sked for them, and CBS is asking them to merely improve upon the numbers for “60 Minutes” in the slot, they could stick around awhile.

  • UPN’s decision to slot a repeat of “America’s Next Top Model” had some insiders scratching their head, but it figures to provide the best lead-in possible for new drama “Sex, Lies and Secrets” (another lame title).

Net can always shift the “Model” repeat to Thursday if its revamped comedy lineup there fails to click, but if “Sex” bombs, the net could be in real Tuesday trouble.

  • NBC’s best hope for the fall may be Monday sea-monster drama “Fathom,” which slides in the “Fear Factor” slot and could do decent biz with young adults and families. If it can click and provide a more compatible lead-in for “Las Vegas,” the Peacock could be very competitive on the night.

  • Three dramas with loyal but small overall audiences — Fox’s “The OC,” ABC’s “Alias” and the WB’s “Smallville” — will do battle in a tough Thursday 8 o’clock showdown. Don’t expect any bailouts here, as each smells blood with NBC’s laffers struggling in the hour and CBS’ “Survivor” past its peak (though still a top-10 hit).

“Alias,” more of a 25-54 show, would seem to be new competish for “Survivor,” while “Smallville” will cross paths more with the “OC” aud.

  • At the WB, the return of “Charmed” to its Sunday-at-8 slot was a mild surprise, but it still performs well enough and deserves a sendoff season.

Still, with “Reba” repeats at 7, “Blue Collar TV” at 9 and the Frog’s comedy development looking better than recent years, a switch to femme-focused laffers at 8 sometime soon is definitely a possibility.

Ace in the hole for the Frog, though, might be unscripted skein “Beauty and the Geek,” a delightful entry that bows this week. Net may at long last have the reality show it needs to boost a troubled timeslot.