A six-year run of double-digit percentage increases in Fairfax County home assessments came to an abrupt end yesterday, as notices mailed to taxpayers showed that their properties have lost value for the first time since 1998.

The good news for county residents is that their property tax bills, which have grown 89 percent since 2001, are also likely to show an actual, if modest, decline. Under the budget proposed yesterday by County Executive Anthony H. Griffin, the tax on a home worth $542,744 -- now the average value of all residential property in Fairfax -- would be $4,830, $16 less than in the current fiscal year.

The drop in assessments was minuscule -- about three-tenths of 1 percent -- but is further evidence of a dramatic softening of the regional housing market in the past year. It also means less money for a county government dependent on property taxes for nearly 60 percent of its operating budget.

Fairfax's falling assessments are consistent with declines reported by other Northern Virginia localities in recent weeks. In Loudoun County, the average assessed value of a single-family home dropped 7.1 percent. Preliminary estimates show a 4 percent drop in Prince William County. Arlington County housing values are down eight-tenths of a percent, and Alexandria's average fell about 3 percent.

Maryland and the District will continue riding the wave of robust increases in value. Maryland, which assesses a third of its properties every year, reports that home values rose 59.4 percent from 2003 through 2006. District assessments, although done annually, usually lag behind market values by a couple of years. Property values in the District are expected to continue to reflect the hot commercial and residential markets of 2005, officials said in December.

The new Fairfax valuations are contained in the 349,351 assessment notices mailed to county taxpayers yesterday. Douglas W. Mumma, an eight-year resident of the Fairfax Station neighborhood, will see the value of his home decline 7 percent, from $809,550 to $752,310. But Mumma said he is less concerned about assessments, which he regards as inflated, than about the rate of county spending. "It's the spending that's more worrisome," Mumma said. "Are they going to bring the tax rate back up to pay for what they're spending?"

The $3.3 billion Fairfax budget presented yesterday by Griffin reflects Northern Virginia's new economic landscape. Although it leaves county services essentially intact, the spending plan for the fiscal year beginning July 1 calls for no new programs. It also retains the current tax rate -- 89 cents per $100 of assessed value -- which officials regularly reduced during the fat revenue years.

County schools, which asked for a 5.1 percent increase over last year's appropriation, received 4 percent, for a total of about $1.59 billion, under Griffin's plan. School officials probably will attempt to obtain a bigger increase.

Superintendent Jack D. Dale said that although he was "fully aware" of the challenges posed by the stagnant housing market, he would probably begin discussions with the board about additional funds to establish full-day kindergarten in all schools.

"The question is how aggressive we can be for that," Dale said.

Overall county spending under Griffin's plan would increase by 3.3 percent.

Board of Supervisors Chairman Gerald E. Connolly (D) said prudent management of the property tax windfalls of recent years has enabled the county to avoid cuts. By cutting the tax rate from $1.23 to 89 cents since 2002, the county restrained spending.

"This is a soft-landing budget," Connolly said. "We didn't develop the appetite for all that extra revenue."

Griffin proposes to further cushion the landing by imposing a 2 percent across-the-board reduction in the personnel budgets of county departments and agencies. The plan calls for no layoffs or pay cuts, but the county hopes to save $16.3 million by not filling positions that become vacant.

Should the residential real estate market remain stagnant, however, new difficulties could surface. Griffin enjoyed several advantages in assembling this year's budget that may not be available in 2008.

Fairfax had the benefit of $33 million in unspent funds it was able to carry over from the current budget -- a pot that might not be there in the future. County finances are also bolstered by increases in the value of apartments and commercial and office property. The value of apartments in the county rose 22.5 percent; high-rise office buildings are up nearly 16 percent; and regional shopping malls are assessed at nearly 13 percent more than a year ago. The county's dwindling supply of commercial vacant land rose nearly 15 percent.

"This has made the difference between this being an extremely difficult budget and being able to maintain our programs," Griffin said.

But Griffin warned that increasingly speculative office construction in the county could lead to a glut that depresses values.

The county also faces at least two other issues that could result in major new financial challenges over the next year. Under the Republican-backed transportation package approved Saturday by the General Assembly, Fairfax County would be required to pay for the planning and construction of roads, a responsibility currently borne by the state.

Connolly denounced the provision yesterday as a "poison pill," and he called for its removal from the legislation. The board voted to ask Gov. Timothy M. Kaine (D) to veto the package if the new road obligations remained.

The county also faces the potential loss of $17 million in schools funding because of a dispute with the U.S. Department of Education over reading tests given to thousands of immigrant children.

Griffin's budget will be reviewed and adjusted by the Board of Supervisors in a series of hearings before final adoption April 30.