Maryland's Acting Gov. Blair Lee III yesterday signed into law three property-tax relief bills that had been considered the cornerstone of the most important property-tax relief legislation enacted by during the 1978 General Assembly session.

Also signed into a law yesterday was a bill limiting the ability of utility companies to pass on automatically to their customers any increases in their fuel costs, and a bill to change the site of a proposed state prison from a warehouse site in East Baltimore to a South Baltimore park.

The tax package is designed to offer some relief to all of Maryland's homeowners, who have watched their tax bills climb steadily over the past few years as a tight real estate market pushed up property values.

Potentially the most tax relief is offered in a bill which gives homeowners a one-time only 10 percent reduction in their tax assessments. This represents a potential $44 million saving for the state's 850,000 homeowners - but only if local governments don't raise their tax rates.

A second bill signed into law is designed to help low-and moderate-income homeowners by expanding the current program of tax credits for the elderly and disabled. A total of $30 million in tax credits will be available. Homeowners under age 60 may qualify for up to $450 in credits; those over 60 can qualify for up to $900 in tax credits.